Positive resist composition and method of forming resist pattern

ABSTRACT

A positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the component (A) including a polymeric compound (A1) having an acid dissociable, dissolution inhibiting group in the structure thereof and including a structural unit (a0) having an —SO 2 — containing cyclic group on the terminal of the side chain, and the component (B) including an acid generator (B1) containing a compound represented by general formula (b1-1) (R 0  represents a hydrocarbon group of 1 to 12 carbon atoms which may have a substituent, provided that the carbon atom adjacent to the sulfur atom within the —SO 3   −  group has no fluorine atom bonded thereto, and Z +  represents an organic cation).
 
R 0 —SO 3   − Z +   (b1-1)

TECHNICAL FIELD

The present invention relates to a positive resist composition and amethod of forming a resist pattern using the positive resistcomposition.

Priority is claimed on Japanese Patent Application No. 2009-058738,filed Mar. 11, 2009, the content of which is incorporated herein byreference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

A resist material in which the exposed portions become soluble in adeveloping solution is called a positive-type, and a resist material inwhich the exposed portions become insoluble in a developing solution iscalled a negative-type.

In recent years, in the production of semiconductor elements and liquidcrystal display elements, advances in lithography techniques have leadto rapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening thewavelength of the exposure light source. Conventionally, ultravioletradiation typified by g-line and i-line radiation has been used, butnowadays KrF excimer lasers and ArF excimer lasers are starting to beintroduced in mass production. Furthermore, research is also beingconducted into lithography techniques that use an exposure light sourcehaving a wavelength shorter than these excimer lasers, such as F₂excimer lasers, electron beam, extreme ultraviolet radiation (EUV), andX-ray.

Resist materials for use with these types of exposure light sourcesrequire lithography properties such as a high resolution capable ofreproducing patterns of minute dimensions, and a high level ofsensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemicallyamplified composition is used, which includes a base material componentthat exhibits a changed solubility in an alkali developing solutionunder the action of acid and an acid generator that generates acid uponexposure.

For example, a chemically amplified positive resist contains, as a basecomponent (base resin), a resin which exhibits increased solubility inan alkali developing solution under action of acid, and an acidgenerator is typically used. If the resist film formed using the resistcomposition is selectively exposed during formation of a resist pattern,then within the exposed portions, acid is generated from the acidgenerator, and the action of this acid causes an increase in thesolubility of the resin component in an alkali developing solution,making the exposed portions soluble in the alkali developing solution.

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowwidely used as base resins for resists that use ArF excimer laserlithography, as they exhibit excellent transparency in the vicinity of193 nm (for example, see Patent Document 1).

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and the methacrylate having a methyl groupbonded to the α-position.

On the other hand, as acid generators usable in a chemically amplifiedresist composition, various types have been proposed including, forexample, onium salt acid generators such as iodonium salts and sulfoniumsalts; oxime sulfonate acid generators; diazomethane acid generators;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators.

Currently, as acid generators, onium salt acid generators having anonium ion such as triphenylsulfonium as the cation moiety are used. Asthe anion moiety for onium salt acid generators, an alkylsulfonate ionor a fluorinated alkylsulfonate ion in which part or all of the hydrogenatoms within the aforementioned alkylsulfonate ion has been substitutedwith fluorine atoms is typically used (for example, see Patent Document2).

DOCUMENTS OF RELATED ART

[Patent Document]

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385

[Patent Document 2] Japanese Unexamined Patent Application, FirstPublication No. 2005-37888

SUMMARY OF THE INVENTION

In recent years, as requirements for high resolution increase withprogress in the miniaturization of resist patterns, formation of resistpatterns having excellent shape has been demanded.

The present invention takes the above circumstances into consideration,with an object of providing a positive resist composition which enablesformation of a resist pattern having an excellent shape, and a method offorming a resist pattern.

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a positiveresist composition including a base component (A) which exhibitsincreased solubility in an alkali developing solution under action ofacid and an acid-generator component (B) which generates acid uponexposure, the base component (A) including a polymeric compound (A1)having an acid dissociable, dissolution inhibiting group in thestructure thereof and including a structural unit (a0) represented bygeneral formula (a0-1) shown below, and the acid-generator component (B)including an acid generator (B1) containing a compound represented bygeneral formula (b1-1) shown below.

In formula (a0-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R²represents a divalent linking group; and R³ represents a cyclic groupcontaining an —SO₂— group within the ring skeleton thereof.[Chemical Formula 2.]R⁰—SO₃ ⁻Z⁺  (b1-1)In formula (b1-1), R⁰ represents a hydrocarbon group of 1 to 12 carbonatoms which may have a substituent, with the provision that the carbonatom adjacent to the sulfur atom within the —SO₃ ⁻ group has no fluorineatom bonded thereto; and Z⁺ represents an organic cation.

A second aspect of the present invention is a method of forming a resistpattern, including applying a positive resist composition according tothe first aspect to a substrate to form a resist film, subjecting theresist film to exposure, and subjecting the resist film to alkalideveloping to form a resist pattern.

In the present description and claims, an “alkyl group” includes linear,branched or cyclic, monovalent saturated hydrocarbon, unless otherwisespecified.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified.

A “lower alkyl group” is an alkyl group of 1 to 5 carbon atoms.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

The term “aliphatic” is a relative concept used in relation to the term“aromatic”, and defines a group or compound that has no aromaticity.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (polymer, copolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there are provided a positive resistcomposition which enable formation of a resist pattern having anexcellent shape, and a method of forming a resist pattern using thesame.

DETAILED DESCRIPTION OF THE INVENTION

<<Positive Resist Composition>>

The positive resist composition according to the first aspect of thepresent invention includes a base component (A) which exhibits increasedsolubility in an alkali developing solution under action of acid(hereafter, referred to as “component (A)”) and an acid-generatorcomponent (B) which generates acid upon exposure (hereafter, referred toas “component (B)”).

In the positive resist composition, when radial rays are irradiated(when exposure is conducted), acid is generated from the component (B),and the solubility of the component (A) in an alkali developing solutionis increased by the action of the generated acid. Therefore, in theformation of a resist pattern, by conducting selective exposure of aresist film formed by using the positive resist composition of thepresent invention, the solubility of the exposed portions in an alkalideveloping solution is increased, whereas the solubility of theunexposed portions in an alkali developing solution is unchanged, andhence, a resist pattern can be formed by alkali developing.

It is preferable that the positive resist composition of the presentinvention further includes a nitrogen-containing organic compound (D)(hereafter referred to as the component (D)).

<Component (A)>

In the present invention, the term “base component” refers to an organiccompound capable of forming a film.

As the base component, an organic compound having a molecular weight of500 or more can be preferably used. When the organic compound has amolecular weight of 500 or more, the film-forming ability is improved,and a resist pattern of nano level can be easily formed.

The “organic compound having a molecular weight of 500 or more” whichcan be used as a base component is broadly classified into non-polymersand polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a non-polymerhaving a molecular weight in the range of 500 to less than 4,000 isreferred to as a low molecular weight compound.

As a polymer, any of those which have a molecular weight of 2,000 ormore is used. Hereafter, a polymer having a molecular weight of 2,000 ormore is referred to as a polymeric compound. With respect to a polymericcompound, the “molecular weight” is the weight average molecular weightin terms of the polystyrene equivalent value determined by gelpermeation chromatography (GPC). Hereafter, a polymeric compound isfrequently referred to simply as a “resin”.

In the present invention, the component (A) includes a polymericcompound (A1) (hereafter, referred to as “component (A1)”) having anacid dissociable, dissolution inhibiting group in the structure thereofand including a structural unit (a0) represented by general formula(a0-1).

[Component (A1)]

The component (A1) is a polymeric compound having an acid dissociable,dissolution inhibiting group in the structure thereof and including astructural unit (a0).

The component (A1) preferably includes a structural unit (a1) derivedfrom an acrylate ester containing an acid dissociable, dissolutioninhibiting group, excluding the structural unit (a0).

It is preferable that the component (A1) further include a structuralunit (a2) derived from an acrylate ester containing a lactone-containingcyclic group.

It is preferable that the component (A1) further include a structuralunit (a3) derived from an acrylate ester containing a polargroup-containing aliphatic hydrocarbon group.

(Structural Unit (a0))

In general formula (a0-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group for R, a linear or branched alkyl group of 1 to 5carbon atoms is preferable, and specific examples thereof include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group.

The halogenated alkyl group for R is a group in which part or all of thehydrogen atoms of the aforementioned alkyl group has been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In general formula (a0-1), R² represents a divalent linking group.

Preferable examples of R² include a divalent hydrocarbon group which mayhave a substituent, and a divalent linking group containing a heteroatom.

Divalent Hydrocarbon Group which May have a Substituent

With respect to R², the hydrocarbon group “has a substituent” means thatpart or all of the hydrogen atoms within the hydrocarbon group has beensubstituted with a group or an atom other than a hydrogen atom.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be saturated or unsaturated. Ingeneral, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatichydrocarbon group) may or may not have a substituent. Examples ofsubstituents include a fluorine atom, a fluorinated alkyl group of 1 to5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group (a group in which twohydrogen atoms have been removed from an aliphatic hydrocarbon ring),and a group in which the cyclic aliphatic hydrocarbon group is bonded tothe terminal of the aforementioned chain-like aliphatic hydrocarbongroup or interposed within the aforementioned chain-like aliphatichydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group.

As the monocyclic group, a group in which two hydrogen atoms have beenremoved from a monocycloalkane of 3 to 6 carbon atoms is preferable.Examples of the monocycloalkane include cyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent.

Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

Examples of aromatic hydrocarbon groups include a divalent aromatichydrocarbon group in which one hydrogen atom has been removed from abenzene ring of a monovalent aromatic hydrocarbon group such as a phenylgroup, a biphenyl group, a fluorenyl group, a naphthyl group, an anthrylgroup or a phenanthryl group;

an aromatic hydrocarbon group in which part of the carbon atomsconstituting the ring of the aforementioned divalent aromatichydrocarbon group has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom; and

and an aromatic hydrocarbon group in which one hydrogen atom has beenremoved from a benzene ring of an arylalkyl group such as a benzylgroup, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethylgroup, a 1-naphthylethyl group or a 2-naphthylethyl group.

The aromatic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

Divalent Linking Group Containing a Hetero Atom

With respect to the “divalent linking group containing a hetero atom”for R², a hetero atom refers to an atom other than carbon and hydrogen,and examples thereof include an oxygen atom, a nitrogen atom, a sulfuratom and a halogen atom.

Specific examples of the divalent linking group containing a hetero atominclude —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —NH—,—NR⁰⁴— (R⁰⁴ represents a substituent such as an alkyl group or an acylgroup), —NH—C(═O)—, ═N—, —S—, —S(═O)₂—, and —S(═O)₂—O—. Further, acombination of any one of these “divalent linking groups containing ahetero atom” with a divalent hydrocarbon group can also be used. Asexamples of the divalent hydrocarbon group, the same groups as thosedescribed above for the hydrocarbon group which may have a substituentcan be given, and a linear or branched aliphatic hydrocarbon group ispreferable.

In the —NR⁰⁴— group, R⁰⁴ represents a substituent such as an alkyl groupor an acyl group. The substituent (an alkyl group, an acyl group or thelike) preferably has 1 to 10 carbon atoms, more preferably 1 to 8, andmost preferably 1 to 5.

R² may or may not have an acid dissociable portion in the structurethereof.

An “acid dissociable portion” refers to a portion within the R² groupwhich is dissociated from the group by action of acid generated uponexposure. When the R² group has an acid dissociable portion, itpreferably has an acid dissociable portion having a tertiary carbonatom.

In the present invention, as the divalent linking group for R², analkylene group, a divalent aliphatic cyclic group or a divalent linkinggroup containing a hetero atom is preferable. Among these, an alkylenegroup is particularly desirable.

When R² represents an alkylene group, it preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3. Specific examples of alkylene groups include theaforementioned linear alkylene groups and branched alkylene groups.

When R² represents a divalent aliphatic cyclic group, as the aliphaticcyclic group, the same aliphatic cyclic groups as those described abovefor the “aliphatic hydrocarbon group containing a ring in the structurethereof” can be used.

As the aliphatic cyclic group, a group in which two hydrogen atoms havebeen removed from cyclopentane, cyclohexane, norbornane, isobornane,adamantane, tricyclodecane or tetracyclododecane is particularlydesirable.

When R² represents a divalent linking group containing a hetero atom,preferable examples of the divalent linking group containing a heteroatom include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NR⁰⁴—(R⁰⁴ represents a substituent such as an alkyl group or an acyl group),—S—, —S(═O)₂—, —S(═O)₂—O—, a group represented by the formula -A-O—B—,and a group represented by the formula -[A-C(═O)—O]_(q)—B—. Herein, eachof A and B independently represents a divalent hydrocarbon group whichmay have a substituent, and q represents an integer of 0 to 3.

In the group represented by the formula -A-O—B— or -[A-C(═O)—O]_(q)—B—,each of A and B independently represents a divalent hydrocarbon groupwhich may have a substituent.

Examples of divalent hydrocarbon groups for A and B which may have asubstituent include the same groups as those described above for the“divalent hydrocarbon group which may have a substituent” usable as R².

As A, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As B, a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula -[A-C(═O)—O]_(q)—B—, qrepresents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

In general formula (a0-1), R³ represents a cyclic group containing —SO₂—within the ring skeleton thereof. More specifically, R³ is a cyclicgroup in which the sulfur atom (S) within the —SO₂— group forms part ofthe ring skeleton thereof.

The cyclic group for R³ refers to a cyclic group including a ring thatcontains —SO₂— within the ring skeleton thereof, and this ring iscounted as the first ring. A cyclic group in which the only ringstructure is the ring that contains —SO₂— in the ring skeleton thereofis referred to as a monocyclic group, and a group containing other ringstructures is described as a polycyclic group regardless of thestructure of the other rings. The cyclic group for R³ may be either amonocyclic group or a polycyclic group.

As R³, a cyclic group containing —O—SO₂— within the ring skeletonthereof, i.e., a sultone ring in which —O—S— within the —O—SO₂— groupforms part of the ring skeleton thereof is particularly desirable.

The cyclic group for R³ preferably has 3 to 30 carbon atoms, morepreferably 4 to 20, still more preferably 4 to 15, and most preferably 4to 12.

Herein, the number of carbon atoms refers to the number of carbon atomsconstituting the ring skeleton, excluding the number of carbon atomswithin a substituent.

The cyclic group for R³ may be either an aliphatic cyclic group or anaromatic cyclic group, and is preferably an aliphatic cyclic group.

Examples of aliphatic cyclic groups for R³ include the aforementionedcyclic aliphatic hydrocarbon groups in which part of the carbon atomsconstituting the ring skeleton thereof has been substituted with —SO₂—or —O—SO₂—.

More specifically, examples of monocyclic groups include amonocycloalkane in which one hydrogen atom have been removed therefromand a —CH₂— group constituting the ring skeleton thereof has beensubstituted with —SO₂—; and a monocycloalkane in which one hydrogen atomhave been removed therefrom and a —CH₂—CH₂— group constituting the ringskeleton thereof has been substituted with —O—SO₂—. Examples ofpolycyclic groups include a polycycloalkane (a bicycloalkane, atricycloalkane, a tetracycloalkane or the like) in which one hydrogenatom have been removed therefrom and a —CH₂— group constituting the ringskeleton thereof has been substituted with —SO₂—; and a polycycloalkanein which one hydrogen atom have been removed therefrom and a —CH₂—CH₂—group constituting the ring skeleton thereof has been substituted with—O—SO₂—.

The cyclic group for R³ may have a substituent. Examples of thesubstituent include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group. R″ represents ahydrogen atom or an alkyl group.

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

As the alkoxy group for the substituent, an alkoxy group of 1 to 6carbon atoms is preferable. Further, the alkoxy group is preferably alinear alkoxy group or a branched alkyl group. Specific examples of thealkoxy group include the aforementioned alkyl groups for the substituenthaving an oxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As examples of the halogenated lower alkyl group for the substituent,groups in which part or all of the hydrogen atoms of the aforementionedalkyl groups for the substituent have been substituted with theaforementioned halogen atoms can be given. As the halogenated alkylgroup, a fluorinated alkyl group is preferable, and a perfluoroalkylgroup is particularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ preferably represents ahydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of R³ include groups represented by generalformulas (3-1) to (3-4) shown below.

In the formulas, A′ represents an oxygen atom, a sulfur atom, or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; p represents an integer of 0 to 2; and R⁸ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulas (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—), or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or interposed within the alkylgroup. Specific examples of such alkylene groups include —O—CH₂—,—CH₂—O—CH₂—, —S—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

p represents an integer of 0 to 2, and is most preferably 0.

When p is 2, the plurality of R⁸ may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, halogenatedalkyl group, hydroxyl group, —COOR″, —OC(═O)R″, hydroxyalkyl group andcyano group for R⁸, the same alkyl groups, alkoxy groups, halogenatedalkyl groups, halogenated alkyl groups, hydroxyl groups, —COOR″,—OC(═O)R″, hydroxyalkyl groups and cyano groups as those described aboveas the substituent which the cyclic group for R³ may have can be used.

Specific examples of the cyclic groups represented by general formulas(3-1) to (3-4) are shown below. In the formulas shown below, “Ac”represents an acetyl group.

Among the examples shown above, as R³, a cyclic group represented bygeneral formula (3-1), (3-3) or (3-4) above is preferable, and a cyclicgroup represented by general formula (3-1) above is particularlydesirable.

More specifically, as R³, it is preferable to use at least one cyclicgroup selected from the group consisting of cyclic groups represented bychemical formulas (3-1-1), (3-1-18), (3-3-1) and (3-4-1) above, and acyclic group represented by chemical formula (3-1-1) above isparticularly desirable.

In the present invention, as the structural unit (a0), a structural unitrepresented by general formula (a0-1-11) shown below is particularlydesirable.

In the formula, R is the same as defined above; R⁰² represents a linearor branched alkylene group or -A-C(═O)—O—B— (wherein A and B are thesame as defined above); and A′ is the same as defined above.

The linear or branched alkylene group for R⁰² preferably has 1 to 10carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,still more preferably 1 to 3, and most preferably 1 or 2.

In the -A-C(═O)—O—B— group, each of A and B preferably represents alinear or branched alkylene group, more preferably an alkylene group of1 to 5 carbon atoms, and most preferably a methylene group or anethylene group. Specific examples thereof include—(CH₂)₂—C(═O)—O—(CH₂)₂—, and —(CH₂)₂—O—C(═O)—(CH₂)₂—.

A′ is preferably a methylene group, an oxygen atom (—O—) or a sulfuratom (—S—).

As the structural unit (a0), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In terms of achieving an excellent shape for a resist pattern formedusing a positive resist composition containing the component (A1) andexcellent lithography properties such as exposure margin (EL margin),line width roughness (LWR) and the like, the amount of the structuralunit (a0) within the component (A1), based on the combined total of allstructural units constituting the component (A1) is preferably 1 to 60mol %, more preferably 5 to 55 mol %, still more preferably 10 to 50 mol%, and most preferably 15 to 45 mol %.

The component (A1) has an acid dissociable, dissolution inhibiting groupwithin the structure thereof.

The acid dissociable, dissolution inhibiting group is a group having analkali dissolution-inhibiting effect that renders the entire component(A1) insoluble in an alkali developing solution prior to dissociation,and is dissociated from the component (A1) by the action of acidgenerated from the component (B) upon exposure. Therefore, when the aciddissociable, dissolution inhibiting group is dissociated from thecomponent (A1), the solubility of the entire component (A1) in an alkalideveloping solution is increased.

The acid dissociable, dissolution inhibiting group can be incorporatedinto the component (A1) by using a structural unit (a0) that contains aportion or group equivalent to an acid dissociable, dissolutioninhibiting group within the structure thereof, or by using a structuralunit other than the structural unit (a0) that contains an aciddissociable, dissolution inhibiting group.

The structural units represented by formulas (3-1-2), (3-1-17) and(3-1-19) described above for the structural unit (a0) contain a cyclicgroup that functions as an acid dissociable, dissolution inhibitinggroup. Furthermore, in a structural unit (a0) in which R² has an aciddissociable portion within the structure thereof, the portion from theacid dissociable portion to the terminal functions as an aciddissociable, dissolution inhibiting group.

When such a structural unit containing an acid dissociable, dissolutioninhibiting group-equivalent group/portion within the structure thereofis used as the structural unit (a0), the component (A1) may consist ofthe structural unit (a0), or may further contain an optional structuralunit (e.g., structural unit (a1), (a2), (a3) or (a4) described later).

On the other hand, when a structural unit containing no aciddissociable, dissolution inhibiting group-equivalent group/portionwithin the structure thereof is used as the structural unit (a0), it isnecessary that the component (A1) contain a structural unit having anacid dissociable, dissolution inhibiting group (e.g., structural unit(a1) described later) in addition to the structural unit (a0).

In the present invention, as a structural unit having an aciddissociable, dissolution inhibiting group, it is preferable to contain astructural unit (a1) derived from an acrylate ester containing an aciddissociable, dissolution inhibiting group, exclusive of the structuralunit (a0).

(Structural Unit (a1))

The structural unit (a1) is a structural unit derived from an acrylateester containing an acid dissociable, dissolution inhibiting group anddoes not fall under the category of the aforementioned structural unit(a0).

As the acid dissociable, dissolution inhibiting group in the structuralunit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire component(A1) insoluble in an alkali developing solution prior to dissociation,and then following dissociation by action of acid, increases thesolubility of the entire component (A1) in the alkali developingsolution. Generally, groups that form either a cyclic or chain-liketertiary alkyl ester with the carboxyl group of the (meth)acrylic acid,and acetal-type acid dissociable, dissolution inhibiting groups such asalkoxyalkyl groups are widely known.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(O)—O—). In thistertiary alkyl ester, the action of acid generally causes cleavage ofthe bond between the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to be constituted of only carbon atomsand hydrogen atoms (not limited to hydrocarbon groups), but ispreferably a hydrocarbon group.

Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

As an example of the aliphatic branched, acid dissociable, dissolutioninhibiting group, for example, a group represented by the formula—C(R⁷¹)(R⁷²)(R⁷³) can be given (in the formula, each of R⁷¹ to R⁷³independently represents a linear alkyl group of 1 to 5 carbon atoms).The group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³)

preferably has 4 to 8 carbon atoms, and specific examples include atert-butyl group, a 2-methyl-2-butyl group, a 2-methyl-2-pentyl groupand a 3-methyl-3-pentyl group. Among these, a tert-butyl group isparticularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot have a substituent. Examples of the substituent include an alkylgroup of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms, afluorine atom, a fluorinated alkyl group of 1 to 5 carbon atoms, and anoxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.

Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated. Furthermore, the “aliphatic cyclic group”is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated alkyl group, may be used. Specific examples include groupsin which one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane or cyclohexane; and groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Further, these groups in which one or more hydrogenatoms have been removed from a monocycloalkane and groups in which oneor more hydrogen atoms have been removed from a polycycloalkane may havepart of the carbon atoms constituting the ring replaced with an etherealoxygen atom (—O—).

Examples of aliphatic cyclic group-containing acid dissociable,dissolution inhibiting groups include

(i) a group which has a tertiary carbon atom on the ring structure of amonovalent aliphatic cyclic group; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

Specific examples of (i) a group which has a tertiary carbon atom on thering structure of a monovalent aliphatic cyclic group include groupsrepresented by general formulas (1-1) to (1-9) shown below.

Specific examples of (ii) a group which has a branched alkylene groupcontaining a tertiary carbon atom, and a monovalent aliphatic cyclicgroup to which the tertiary carbon atom is bonded include groupsrepresented by general formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

As the alkyl group for R¹⁴, a linear or branched alkyl group ispreferable.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

As the alkyl group for R¹⁵ and R¹⁶, the same alkyl groups as those forR¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxy group or hydroxyl group, so as tobe bonded with an oxygen atom. When acid is generated upon exposure, thegenerated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2,more preferably 0 or 1, and most preferably 0.

As the alkyl group of 1 to 5 carbon atoms for R¹′ and R²′, the samealkyl groups of 1 to 5 carbon atoms as those described above for R canbe used, although a methyl group or ethyl group is preferable, and amethyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable, dissolution inhibiting group (p1) is a group represented bygeneral formula (p1-1) shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the alkyl group of 1 to 5 carbon atoms for Y, the same alkyl groupsof 1 to 5 carbon atoms as those for R above can be used.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same groups described above in connection with the“aliphatic cyclic group” can be used.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the R¹⁷ group isbonded to the R¹⁹ group to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable. Itis particularly desirable that either one of R¹⁷ and R¹⁸ be a hydrogenatom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ora methyl group, and an ethyl group is particularly desirable.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto. Such a cyclic group is preferably a 4- to7-membered ring, and more preferably a 4- to 6-membered ring. Specificexamples of the cyclic group include tetrahydropyranyl group andtetrahydrofuranyl group.

Specific examples of acetal-type acid dissociable, dissolutioninhibiting groups include groups represented by formulas (p3-1) to(p3-12) shown below.

In the formulas above, R¹³ represents a hydrogen atom or a methyl group;and g is the same as defined above.

Specific examples of the structural unit (a1) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable, dissolution inhibiting group; Y²represents a divalent linking group; and X² represents an aciddissociable, dissolution inhibiting group.

In general formula (a1-0-1), R is the same as defined for R in generalformula (a0-1).

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

As examples of the divalent linking group for Y², the same groups asthose described above for R² in formula (a0-1) can be given.

As Y², the aforementioned alkylene group, a divalent aliphatic cyclicgroup or a divalent linking group containing a hetero atom described inthe explanation of R² is preferable. Among these, a divalent linkinggroup containing a hetero atom is preferable, and a linear groupcontaining an oxygen atom as a heteratom, e.g., a group containing anester bond is particularly desirable.

More specifically, a group represented by the aforementioned formula-A-O—B— or -A-C(═O)—O—B— is preferable, and a group represented by theformula —(CH₂)_(x)—C(═O)—O—(CH₂)_(y)— is particularly desirable.

x represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

y represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, X′ represents a tertiary alkyl ester-type aciddissociable, dissolution inhibiting group; Y represents an alkyl groupof 1 to 5 carbon atoms or an aliphatic cyclic group; n represents aninteger of 0 to 3; Y² represents a divalent linking group; R is the sameas defined above; and each of R¹′ and R²′ independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ include the same tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups as those described above forX¹.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable, dissolution inhibiting group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the present invention, as the structural unit (a1), a structural unitrepresented by general formula (a1-1-01) shown below which includes theaforementioned formulas (a1-1-1), (a1-1-2) and (a1-1-7) to (a1-1-15) isparticularly desirable in terms of achieving excellent lithographyproperties (e.g. EL margin, LWR, resolution and the like) and anexcellent resist pattern shape.

As a structural unit represented by general formula (a1-1-01) shownbelow, a structural unit represented by general formula (a1-1-101) shownbelow which includes the aforementioned formulas (a1-1-1) and (a1-1-2)is particularly desirable.

In the formulas, R is the same as defined above; each of R⁵⁵ and R¹¹independently represents a linear alkyl group of 1 to 5 carbon atoms;and R⁵⁴ represents a group which forms an aliphatic polycyclic grouptogether with the carbon atom bonded to the R⁵⁴ group.

In general formula (a1-1-01), as the aliphatic polycyclic group formedby R⁵⁴ and the carbon atom to which R⁵⁴ is bonded, the same aliphaticcyclic groups as those described above for the aforementioned tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group andwhich are polycyclic can be used.

Further, it is preferable that the component (A1) include, as thestructural unit (a1), at least one member selected from the groupconsisting of a structural unit represented by general formula (a1-0-11)shown below, a structural unit represented by general formula (a1-0-12)shown below, and a structural unit represented by general formula(a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; R⁵¹ represents an alkyl group; R⁵²represents a group which forms an aliphatic monocyclic group with thecarbon atom to which R⁵² is bonded; R⁵³ represents a branched alkylgroup; R⁵⁴ is the same as defined for R⁵⁴ in general formula (a1-1-01);Y² represents a divalent linking group; and X² represents an aciddissociable, dissolution inhibiting group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R⁵¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group or an ethyl group, and mostpreferably an ethyl group.

As the aliphatic monocyclic group formed by R⁵² and the carbon atoms towhich R⁵² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are monocyclic can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane. The monocycloalkane ispreferably a 3- to 11-membered ring, more preferably a 3- to 8-memberedring, still more preferably a 4- to 6-membered ring, and most preferablya 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ethereal oxygen atom (—O—).

Further, the monocycloalkane may have a substituent such as a loweralkyl group, a fluorine atom or a fluorinated alkyl group.

As an examples of R⁵² constituting such an aliphatic cyclic group, analkylene group which may have an ethereal oxygen atom (—O—) interposedbetween the carbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-1-16) to (a1-1-23). Among these, a structural unitrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by the aforementioned formulas (a1-1-16),(a1-1-17) and (a1-1-20) to (a1-1-23) is preferable. Further, astructural unit represented by general formula (a1-1-02′) shown below isalso preferable.

In the formulas shown below, h is preferably 1 or 2, and most preferably2.

In the formulas, R and R⁵¹ are the same as defined above; and hrepresents an integer of 1 to 3.

In general formula (a1-0-12), as the branched alkyl group for R⁵³, thesame alkyl groups as those described above for R¹⁴ which are branchedcan be used, and an isopropyl group is particularly desirable.

R⁵⁴ is the same as defined for R⁵⁴ in formula (a1-1-01).

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-1-26) to (a1-1-31).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4), and a structural unit represented by formula (a1-3)is preferable.

As a structural unit represented by general formula (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula -A-O—B— or-A-C(═O)—O—B— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; and v represents an integer of 1 to10.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; v represents an integer of 1 to 10;and n′ represents an integer of 0 to 3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociable,dissolution inhibiting group; and n″ represents an integer of 1 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹² is preferably ahydrogen atom.

v is preferably an integer of 1 to 8, more preferably 1 to 5, and mostpreferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulas (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulas (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable, dissolution inhibiting group for X′, the samegroups as those described above can be used. X′ is preferably a tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group, morepreferably the aforementioned group (i) which has a tertiary carbon atomon the ring structure of a monovalent aliphatic cyclic group. Among theaforementioned groups (i), a group represented by general formula (1-1)above is preferable.

n″ is an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable. Among these, a structural unitrepresented by general formula (a1-3-03-1) is preferable, and astructural unit represented by the aforementioned formula (a1-3-29) or(a1-3-30) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; v representsan integer of 1 to 10; w represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

v is preferably an integer of 1 to 5, and most preferably 1 or 2.

w is preferably an integer of 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 25 to 65 mol %. When the amount of the structuralunit (a1) is at least as large as the lower limit of the above-mentionedrange, a pattern can be easily formed using a resist compositionprepared from the component (A1). On the other hand, when the amount ofthe structural unit (a1) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Structural Unit (a2))

The structural unit (a2) is a structural unit derived from an acrylateester containing a lactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

In the present invention, a structural unit derived from an acrylateester containing a lactone-containing cyclic group which falls under thecategory of the aforementioned structural unit (a1) is classified as astructural unit (a1). When the component (A1) is used for forming aresist film, the lactone-containing cyclic group of the structural unit(a2) is effective in improving the adhesion between the resist film andthe substrate, and increasing the compatibility with the developingsolution containing water.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propiolatone, a group in which one hydrogen atom hasbeen removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

In the formulas, R represents a hydrogen atom, a lower alkyl group or ahalogenated lower alkyl group; each R′ independently represents ahydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom oran alkyl group; R²⁹ represents a single bond or a divalent linkinggroup; s″ represents an integer of 0 to 2; A″ represents an oxygen atom,a sulfur atom or an alkylene group of 1 to 5 carbon atoms which maycontain an oxygen atom or a sulfur atom; and m represents 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as defined for R inthe structural unit (a1).

As examples of R′, the same groups as those described above for R⁸ ingeneral formula (3-1) can be given. In terms of industrial availability,R′ is preferably a hydrogen atom.

As examples of A″, the same groups as those described above for A′ ingeneral formula (3-1) can be given.

R²⁹ represents a single bond or a divalent linking group. Examples ofdivalent linking groups include the same divalent linking groups asthose described above for R² in general formula (a0-1). Among these, analkylene group, an ester bond (—C(═O)—O—) or a combination thereof ispreferable. The alkylene group as a divalent linking group for R²⁹ ispreferably a linear or branched alkylene group. Specific examplesinclude the same linear alkylene groups and branched alkylene groups asthose described above for R².

s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below. In the formulas shown below, R^(α)represents a hydrogen atom, a methyl group or a trifluoromethyl group.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) in which s′ is 1 include groups in which the oxygenatom (—O—) within the carbonyloxy group bonded to the carbon atom on theα position and the lactone-containing cyclic group bonded to the oxygenatom has —CH₂—C(═O)—O— or —C(CH₃)₂—C(═O)—O— interposed therebetween.

In the component (A1), as the structural unit (a2), one type ofstructural unit may be used, or two or more types may be used incombination.

In the present invention, it is particularly desirable that thecomponent (A1) contain, as a structural unit (a2), at least onestructural unit selected from the group consisting of a structural unitrepresented by general formula (a2-1) and a structural unit representedby general formula (a2-2).

In terms of improving the adhesion between a substrate and a resist filmformed using a positive resist composition containing the component (A1)and increasing the compatibility with a developing solution, the amountof the structural unit (a2) within the component (A1), based on thecombined total of all structural units constituting the component (A1)is preferably 5 to 70 mol %, more preferably 10 to 65 mol %, still morepreferably 20 to 65 mol %, and most preferably 20 to 45 mol %. Byensuring the above-mentioned range, CDU and the pattern shape can befurther improved.

Further, in terms of achieving excellent lithography properties, theamount of the structural unit (a0) and the structural unit (a2) withinthe component (A1), based on the combined total of all structural unitsconstituting the component (A1) is preferably 1 to 70 mol %, morepreferably 5 to 70 mol %, still more preferably 10 to 65 mol %, and mostpreferably 20 to 65 mol %. By ensuring the above-mentioned range, CDUand the pattern shape can be further improved.

(Structural Unit (a3))

The structural unit (a3) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon group.

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A) is improved, and hence, thecompatibility of the component (A) with the developing solution isimproved. As a result, the alkali solubility of the exposed portionsimproves, which contributes to favorable improvements in the resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which some of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. 1 is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3), one type of structural unit may be used, ortwo or more types may be used in combination.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %. When the amount of the structuralunit (a3) is at least as large as the lower limit of the above-mentionedrange, the effect of using the structural unit (a3) can besatisfactorily achieved. On the other hand, when the amount of thestructural unit (a3) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Other Structural Units)

The component (A1) may also have a structural unit other than theabove-mentioned structural units (a0), (a1), (a2) and (a3), as long asthe effects of the present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as one of the above structural units (a0), (a1), (a2) and(a3) can be used without any particular limitations, and any of themultitude of conventional structural units used within resist resins forArF excimer lasers or KrF excimer lasers (and particularly for ArFexcimer lasers) can be used.

As such a structural unit, a structural unit derived from an acrylateester containing a non-acid-dissociable aliphatic polycyclic group ispreferable.

Examples of this polycyclic group include the same groups as thosedescribed above in connection with the aforementioned structural unit(a1), and any of the multitude of conventional polycyclic groups usedwithin the resin component of resist compositions for ArF excimer lasersor KrF excimer lasers (and particularly for ArF excimer lasers) can beused.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecanyl group,adamantyl group, tetracyclododecanyl group, isobornyl group, andnorbornyl group is particularly desirable. These polycyclic groups maybe substituted with a linear or branched alkyl group of 1 to 5 carbonatoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulas, R is the same as defined above.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

In the present invention, the component (A1) is a polymeric compoundhaving an acid dissociable, dissolution inhibiting group in thestructure thereof and including a structural unit (a0).

As the component (A1), for example, a copolymer including the structuralunit (a0) and the structural unit (a1) is preferable. Examples of such acopolymer include a copolymer consisting of the structural units (a0)and (a1), a copolymer consisting of the structural units (a0), (a1) and(a3), a copolymer consisting of the structural units (a0), (a1) and(a2), and a copolymer consisting of the structural units (a0), (a1),(a2) and (a3).

In the present invention, as the component (A1), a copolymer thatincludes a combination of structural units such as that shown below(polymeric compounds (A1-1) to (A1-7)) is particularly desirable.

In the formula, R, R⁰² and A′ are the same as defined above, wherein theplurality of R may be the same or different from each other; and each ofR²⁰ and R⁵¹′ independently represents an alkyl group.

In the formulas, R, R⁰², A′ and R⁵¹ are the same as defined above;wherein the plurality of R may be the same or different from each other;and R²⁰ represents an alkyl group.

In the formula, R, R⁰² and A′ are the same as defined above, wherein theplurality of R may be the same or different from each other; and R²⁰represents an alkyl group.

In the formula, R, R⁰², A′, R¹⁴, v and w are the same as defined above,wherein the plurality of R may be the same or different from each other;and R²⁰ represents an alkyl group.

In the formula, R, R⁰² and A′ are the same as defined above, wherein theplurality of R may be the same or different from each other; and R²⁰represents an alkyl group.

In the formula, R, R⁰², A′, R⁵¹ and h are the same as defined above,wherein the plurality of R may be the same or different from each other;and R²⁰ represents an alkyl group.

In the formula, R, R⁰², A′, R⁵¹, h, R²⁹, A″ and R′ are the same asdefined above, wherein the plurality of R and R′ may be the same ordifferent from each other; and R²⁰ represents an alkyl group.

In the aforementioned chemical formulas representing the polymericcompounds (A1-1) to (A1-7), as the alkyl group for R²⁰, the same alkylgroups as those described above for R¹⁴ can be mentioned, and ispreferably a linear or branched alkyl group. As the linear alkyl group,a methyl group or an ethyl group is preferable. As the branched alkylgroup, an isopropyl group is preferable.

In the chemical formulas, the alkyl group for R⁵¹ is the same as definedfor the alkyl group represented by R, preferably a methyl group or anethyl group, and most preferably a methyl group.

In the chemical formulas, the alkyl group for R⁵¹′ is the same asdefined for the alkyl group represented by R, preferably a methyl groupor an ethyl group, and most preferably an ethyl group.

In the chemical formulas, A′ is the same as defined for A′ in generalformula (a0-1-11), and is preferably an oxygen atom, a methylene groupor an ethylene group.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)is not particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 5,000 to 20,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, a resist pattern exhibiting ahigh rectangularity can be formed, and various lithography propertiesare improved. Further, the solubility of the base component (A) in anorganic solvent can be improved.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

For example, as a monomer for deriving the structural unit (a0), acompound represented by general formula (a0-1-0) shown below (hereafter,referred to as “compound (a0-1-0)”) can be used.

In general formula (a0-1-0), R, R² and R³ are the same as defined above.

The method for producing the compound (a0-1-0) is not particularlylimited, and the compound (a0-1-0) can be produced by a conventionalmethod.

For example, in the presence of a base, a compound (X-2) represented bygeneral formula (X-2) shown below is added to a solution obtained bydissolving a compound (X-1) represented by general formula (X-1) shownbelow in a reaction solvent, and a reaction is effected to therebyobtain a compound (a0-1-0).

Examples of the base include inorganic bases such as sodium hydride,K₂CO₃ and Cs₂CO₃; and organic bases such as triethylamine,4-dimethylaminopyridine (DMAP) and pyridine. Examples of condensingagents include carbodiimide reagents such asethyldiisopropylaminocarbodiimide hydrochloride (EDCI),dicyclohexylcarboxylmide (DCC), diisopropylcarbodiimide andcarbodiimidazole; tetraethyl pyrophosphate; andbenzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide(Bop reagent).

If desired, an acid may be used. As the acid, any acid generally usedfor dehydration/condensation may be used. Specific examples includeinorganic acids such as hydrochloric acid, sulfuric acid and phosphoricacid; and organic acids such as methanesulfonic acid,trifluoromethanesulfonic acid, benzenesulfonic acid andp-toluenesulfonic acid. These acids can be used individually, or in acombination of two or more.

In the positive resist composition of the present invention, thecomponent (A) may contain “a base component which exhibits increasedsolubility in an alkali developing solution under action of acid” otherthan the component (A1) (hereafter, referred to as “component (A2)”).

The component (A2) is not particularly limited, and any of the multitudeof conventional base components used within chemically amplified resistcompositions (e.g., base resins used within chemically amplified resistcompositions for ArF excimer lasers or KrF excimer lasers, preferablyArF excimer lasers) can be used. For example, as a base resin for ArFexcimer laser, a base resin having the aforementioned structural unit(a1) as an essential component, and optionally the aforementionedstructural units (a2) to (a4) can be used.

As the component (A2), one type of resin may be used, or two or moretypes of resins may be used in combination.

As the component (A), one type may be used, or two or more types ofcompounds may be used in combination.

In the resist composition of the present invention, the amount of thecomponent (A) can be appropriately adjusted depending on the thicknessof the resist film to be formed, and the like.

<Component (B)>

The component (B) includes an acid generator (B1) including a compoundrepresented by general formula (b1-1) shown below (hereafter, this acidgenerator (B1) is referred to as “component (B1)”).[Chemical Formula 50.]R⁰—SO₃ ⁻Z⁺  (b1-1)In formula (b1-1), R⁰ represents a hydrocarbon group of 1 to 12 carbonatoms which may have a substituent, with the provision that the carbonatom adjacent to the sulfur atom within the —SO₃ ⁻ group has no fluorineatom bonded thereto; and Z⁺ represents an organic cation.

In general formula (b1-1), the hydrocarbon group for R⁰ may or may nothave a substituent.

However, the carbon atom adjacent to the sulfur atom within the —SO₃ ⁻group has no fluorine atom bonded thereto. Therefore, upon exposure, thecomponent (B1) generates a sulfonic acid exhibiting a weaker acidstrength than the acid generated from an acid generator in which afluorine atom is bonded to the carbon atom adjacent to the sulfur atomwithin —SO₃ ⁻. As a result, in the present invention, the shape of aresist pattern formed can be improved. Further, the lithographyproperties are also improved.

The substituent preferably contains no fluorine atom, and examplesthereof include a lower alkyl group of 1 to 5 carbon atoms and an oxygenatom (═O).

The hydrocarbon group of 1 to 12 carbon atoms represented by R⁰ may beeither an aliphatic hydrocarbon group or an aromatic hydrocarbon group.By virtue of using a hydrocarbon group of 1 to 12 carbon atoms, therectangularity of the resist pattern is improved.

When the hydrocarbon group for R⁰ is an aliphatic hydrocarbon group, thealiphatic hydrocarbon group may be either saturated or unsaturated, butin general, the aliphatic hydrocarbon group is preferably saturated.

Further, the aliphatic hydrocarbon group may be either a chain-like(linear or branched) hydrocarbon group, or a cyclic hydrocarbon group.

As the chain-like hydrocarbon group, a linear or branched alkyl group ispreferable. The alkyl group preferably has 1 to 10 carbon atoms, morepreferably 1 to 8, and still more preferably 3 to 8.

Specific examples of linear or branched alkyl groups include a methylgroup, an ethyl group, an n-propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group, an n-hexyl group, an n-heptyl groupand an n-octyl group. Among these, a methyl group, an n-propyl group andan n-octyl group are preferable, and an n-octyl group is particularlydesirable.

Specific examples of the component (B1) having a sulfonate ion as theanion moiety in which R⁰ represents a linear or branched alkyl groupinclude onium salts having a cation represented by general formula(I-1), (I-2), (I-5) or (I-6) above as the cation moiety, and a sulfonateion represented by general formula (b1-1-1) shown below as the anionmoiety.[Chemical Formula 51.]C_(a)H_(2a+1)SO₃ ⁻  (b1-1-1)In the formula, a represents an integer of 1 to 10.

In general formula (b1-1-1), a represents an integer of 1 to 10, andpreferably 1 to 8.

Specific examples of sulfonate ions represented by general formula(b1-1-1) include a methanesulfonate ion, an ethanesulfonate ion, ann-propanesulfonate ion, an n-butanesulfonate ion and ann-octanesulfonate ion.

Examples of cyclic hydrocarbon groups as the hydrocarbon group for R⁰include an aliphatic cyclic group and a group in which at least onehydrogen atom within a chain-like hydrocarbon group have beensubstituted with an aliphatic cyclic group (aliphatic cyclicgroup-containing group).

As the “aliphatic cyclic group”, the same aliphatic cyclic groups asthose described above in connection with the acid dissociable,dissolution inhibiting group for the component (A) can be used. Thealiphatic cyclic group preferably has 3 to 12 carbon atoms, and morepreferably 4 to 10.

The aliphatic cyclic group may be either a polycyclic group or amonocyclic group.

As the monocyclic group, a group in which one hydrogen atom has beenremoved from a monocycloalkane of 3 to 6 carbon atoms is preferable, andspecific examples thereof include a cyclopentyl group and a cyclohexylgroup.

The polycyclic group preferably has 7 to 12 carbon atoms, and specificexamples thereof include an adamantyl group, a norbornyl group, anisobornyl group, a tricyclodecanyl group and a tetracyclododecanylgroup.

Among the aforementioned examples, a polycyclic group is preferable, andan adamantyl group, a norbornyl group or a tetracyclododecanyl group ispreferable from an industrial viewpoint. As described above, thesealiphatic cyclic groups may or may not have a substituent.

As the aliphatic cyclic group within the “aliphatic cyclicgroup-containing group”, the same groups as those described above can beused. As the chain-like hydrocarbon group to which the aliphatic cyclicgroup is bonded to form the “aliphatic cyclic group-containing group”, alinear or branched alkyl group is preferable, and a lower alkyl group of1 to 5 carbon atoms is more preferable. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, a tert-butyl group, a pentylgroup, an isopentyl group and a neopentyl group. Among these, a linearalkyl group is preferable, and from industrial viewpoint, a methyl groupor an ethyl group is more preferable.

Specific examples of sulfonate ions in which R⁰ is a cyclic hydrocarbongroup include sulfonate ions represented by formulas (b1-1-21) to(b1-1-26) shown below.

Further, as a sulfonate ion in which R⁰ represents a cyclic hydrocarbongroup, an ion represented by general formula (b1-1-20) shown below isalso preferable.[Chemical Formula 53.]R^(0X)

CH₂

_(r)SO₃ ⁻  (b1-1-20)In general formula (b1-1-20), R^(0X) represents a cyclic alkyl group of4 to 12 carbon atoms that has an oxygen atom (═O) as a substituent; andr represents 0 or 1.

In general formula (b1-1-20), R^(0X) represents a cyclic alkyl group of4 to 12 carbon atoms that has an oxygen atom (═O) as a substituent

The expression “has an oxygen atom as a substituent” means that twohydrogen atoms bonded to a carbon atom constituting the cyclic alkylgroup of 4 to 12 carbon atoms are substituted with an oxygen atom (═O).

The cyclic alkyl group represented by R^(0X) is not particularly limitedas long as it has 4 to 12 carbon atoms, and may be either polycyclic ormonocyclic. Examples thereof include a group in which one hydrogen atomhas been removed from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane. As the monocyclicgroup, a group in which one hydrogen atom has been removed from amonocycloalkane of 3 to 8 carbon atoms is preferable, and specificexamples thereof include a cyclopentyl group, a cyclohexyl group, acycloheptyl group and a cyclooctyl group. The polycyclic grouppreferably has 7 to 12 carbon atoms, and specific examples thereofinclude an adamantyl group, a norbornyl group, an isobornyl group, atricyclodecanyl group and a tetracyclododecanyl group.

As R^(0X), a polycyclic alkyl group of 4 to 12 carbon atoms that has anoxygen atom (═O) as a substituent is preferable. From an industrialviewpoint, a group in which two hydrogen atoms bonded to a carbon atomconstituting an adamantyl group, a norbornyl group or atetracyclododecyl group are substituted with an oxygen atom (═O) ispreferable, and a norbornyl group having an oxygen atom (═O) as asubstituent is particularly desirable.

R^(0X) may have a substituent other than an oxygen atom. As an exampleof such a substituent, a lower alkyl group of 1 to 5 carbon atoms can begiven.

In general formula (b1-1-20), r represents 0 or 1, and preferably 1.

In the present invention, specific examples of a preferable anion moietyfor the compound (b1-1-20) include an anion represented by formula(b1-1-201) shown below and an anion represented by formula (b1-1-202)shown below.

Of these, in terms of the effects of the present invention, acamphorsulfonate ion represented by formula (b1-1-201) shown below ispreferable.

Examples of the aromatic hydrocarbon group as the hydrocarbon group forR⁰ include a phenyl group, a tolyl group, a xylyl group, a mesitylgroup, a phenethyl group and a naphthyl group. As described above, thearomatic hydrocarbon group may or may not have a substituent.

Specific examples of aromatic hydrocarbon groups for R⁰ include groupsrepresented by general formula (b1-1-31) or (b1-1-32) shown below.

In formula (b1-1-31), each of R⁶¹ and R⁶² independently represents analkyl group of 1 to 5 carbon atoms or an alkoxy group of 1 to 5 carbonatoms.

Examples of the alkyl group for R⁶¹ and R⁶² include a methyl group, anethyl group, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group. Among these, a methyl group is particularlydesirable.

Examples of the alkoxy group for R⁶¹ and R⁶² include a methoxy group, anethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy groupand a tert-butoxy group. Among these, a methoxy group or an ethoxy groupis particularly desirable.

Each of d and e independently represents an integer of 0 to 4,preferably 0 to 2, and most preferably 0.

If there are two or more of the R⁶¹ group and/or R⁶² group, as indicatedby the value d and/or e, then the two or more of the R⁶¹ group and/orthe R⁶² group may be the same or different from each other.

In formula (b1-1-32), R⁶³ represents an alkyl group of 1 to 5 carbonatoms or an alkoxy group of 1 to 5 carbon atoms.

Examples of the alkyl group for R⁶³ include a methyl group, an ethylgroup, an n-propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group. Among these, a methyl group is particularlydesirable.

Examples of the alkoxy group for R⁶³ include a methoxy group, an ethoxygroup, an n-propoxy group, an isopropoxy group, an n-butoxy group and atert-butoxy group. Among these, a methoxy group or an ethoxy group isparticularly desirable.

f represents an integer of 0 to 3, preferably 1 or 2, and mostpreferably 1.

If there are two or more of the R⁶³ group, as indicated by the value f,the two or more of the R⁶³ group may be the same or different from eachother.

In general formula (b1-1), as the organic cation for Z⁺, there is noparticular limitation, and any of those conventionally known as cationmoiety for an onium salt-based acid generator can be appropriatelyselected for use. As the cation moiety, a sulfonium ion or an iodoniumion is preferable, and a sulfonium ion is particularly desirable.

Specific examples of the organic cation for Z⁺ include cationsrepresented by general formula (I-1) or (I-2) shown below.

In formula (I-1), each of R¹″ to R³″ independently represents an arylgroup which may have a substituent or an alkyl group which may have asubstituent, with the provision that at least one of R″ to R³″represents an aryl group, and two of R″ to R³″ in formula (I-1) may bebonded to each other to form a ring with the sulfur atom. In formula(I-2), R⁵″ and R⁶″ each independently represent an aryl group which mayhave a substituent or an alkyl group which may have a substituent, withthe provision that and at least one of R⁵″ and R⁶″ represents an arylgroup.

In formula (I-1), each of R″ to R³″ independently represents an arylgroup or an alkyl group. In formula (I-1), two of R¹″ to R³″ may bebonded to each other to form a ring with the sulfur atom.

Further, among R¹″ to R³″, at least one group represents an aryl group.Among R¹″ to R³″, two or more groups are preferably aryl groups, and itis particularly desirable that all of R¹″ to R³″ are aryl groups.

The aryl group for R¹″ to R³″ is not particularly limited. Examplesthereof include an unsubstituted aryl group having 6 to 20 carbon atoms,a substituted aryl group in which part or all of the hydrogen atoms ofthe aforementioned unsubstituted aryl group has been substituted withalkyl groups, alkoxy groups, alkoxyalkyloxy groups,alkoxycarbonylalkyloxy groups, halogen atoms or hydroxyl groups, and agroup represented by the formula —(R⁴′)—C(═O)—R⁵′. R⁴′ represents analkylene group of 1 to 5 carbon atoms. R⁵′ represents an aryl group. Asthe aryl group for R⁵′, the same aryl groups as those described abovefor R¹″ to R³″ can be used.

The unsubstituted aryl group is preferably an aryl group having 6 to 10carbon atoms because it can be synthesized at a low cost. Specificexamples thereof include a phenyl group and a naphthyl group.

The alkyl group as the substituent for the substituted aryl group ispreferably an alkyl group having 1 to 5 carbon atoms, and a methylgroup, an ethyl group, a propyl group, an n-butyl group, or a tert-butylgroup is particularly desirable.

The alkoxy group as the substituent for the substituted aryl group ispreferably an alkoxy group having 1 to 5 carbon atoms, and a methoxygroup, an ethoxy group, an n-propoxy group, an iso-propoxy group, ann-butoxy group or a tert-butoxy group is particularly desirable.

The halogen atom as the substituent for the substituted aryl group ispreferably a fluorine atom.

Examples of the alkoxyalkyloxy group as the substituent for thesubstituted aryl group include a group represented by a general formula—O—C(R⁴⁷)(R⁴⁸)—O—R⁴⁹ (in the formula, each of R⁴⁷ and R⁴⁸ independentlyrepresent a hydrogen atom or a linear or branched alkyl group; and R⁴⁹represents an alkyl group).

The alkyl group for R⁴⁷ and R⁴⁸ preferably has 1 to 5 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable.

It is preferable that at least one of R⁴⁷ and R⁴⁸ be a hydrogen atom. Itis particularly desirable that at least one of R⁴⁷ and R⁴⁸ be a hydrogenatom, and the other be a hydrogen atom or a methyl group.

The alkyl group for R⁴⁹ preferably has 1 to 15 carbon atoms, and may belinear, branched or cyclic.

The linear or branched alkyl group for R⁴⁹ preferably has 1 to 5 carbonatoms. Examples thereof include a methyl group, an ethyl group, a propylgroup, an n-butyl group and a tert-butyl group.

The cyclic alkyl group for R⁴⁹ preferably has 4 to 15 carbon atoms, morepreferably 4 to 12, and most preferably 5 to 10. Specific examplesthereof include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane or a polycycloalkane such as abicycloalkane, tricycloalkane or tetracycloalkane, and which may or maynot be substituted with an alkyl group of 1 to 5 carbon atoms, afluorine atom or a fluorinated alkyl group. Examples of themonocycloalkane include cyclopentane and cyclohexane. Examples ofpolycycloalkanes include adamantane, norbornane, isobornane,tricyclodecane and tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

An example of the alkoxycarbonylalkyloxy group as the substituent forthe substituted aryl group includes a group represented by a generalformula —O—R⁵⁰—C(═O)—O—R⁵⁶ (in the formula, R⁵⁰ represents a linear orbranched alkylene group; and R⁵⁶ represents a tertiary alkyl group.)

The linear or branched alkylene group for R⁵⁰ preferably has 1 to 5carbon atoms, and examples thereof include a methylene group, anethylene group, a trimethylene group, a tetramethylene group and a1,1-dimethylethylene group.

Examples of the tertiary alkyl group for R⁵⁶ include a2-methyl-2-adamantyl group, a 2-ethyl-2-adamantyl group, a1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a1-methyl-1-cyclohexyl group, a 1-ethyl-1-cyclohexyl group, a1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropylgroup, a 1-(1-adamantyl)-1-methylbutyl group, a1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethylgroup, a 1-(1-cyclopentyl)-1-methylpropyl group, a1-(1-cyclopentyl)-1-methylbutyl group, a1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethylgroup, a 1-(1-cyclohexyl)-1-methylpropyl group, a1-(1-cyclohexyl)-1-methylbutyl group, a 1-(1-cyclohexyl)-1-methylpentylgroup, a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

The aryl group for each of R¹″ to R³″ is preferably a phenyl group or anaphthyl group.

The alkyl group for R¹″ to R³″ is not particularly limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, an n-pentyl group, acyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, anda decanyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom, it is preferable that the two of R¹″ to R³″ form a 3 to10-membered ring including the sulfur atom, and it is particularlydesirable that the two of R¹″ to R³″ form a 5 to 7-membered ringincluding the sulfur atom.

When two of R¹″ to R³″ are bonded to each other to form a ring with thesulfur atom, the remaining one of R¹″ to R³″ is preferably an arylgroup. As examples of the aryl group, the same as the above-mentionedaryl groups for R¹″ to R³″ can be given.

Specific examples of cation moiety represented by general formula (I-1)include triphenylsulfonium, (3,5-dimethylphenyl)diphenylsulfonium,(4-(2-adamantoxymethyloxy)-3,5-dimethylphenyl)diphenylsulfonium,(4-(2-adamantoxymethyloxy)phenyl)diphenylsulfonium,(4-(tert-butoxycarbonylmethyloxy)phenyl)diphenylsulfonium,(4-(tert-butoxycarbonylmethyloxy)-3,5-dimethylphenyl)diphenylsulfonium,(4-(2-methyl-2-adamantyloxycarbonylmethyloxy)phenyl)diphenylsulfonium,(4-(2-methyl-2-adamantyloxycarbonylmethyloxy)-3,5-dimethylphenyl)diphenylsulfonium,tri(4-methylphenyl)sulfonium, dimethyl(4-hydroxynaphthyl)sulfonium,monophenyldimethylsulfonium, diphenylmonomethylsulfonium,(4-methylphenyl)diphenylsulfonium, (4-methoxyphenyl)diphenylsulfonium,tri(4-tert-butyl)phenylsulfonium,diphenyl(1-(4-methoxy)naphthyl)sulfonium, di(1-naphthyl)phenylsulfonium,1-phenyltetrahydrothiophenium, 1-(4-methylphenyl)tetrahydrothiophenium,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiophenium,1-(4-methoxynaphthalene-1-yl)tetrahydrothiophenium,1-(4-ethoxynaphthalene-1-yl)tetrahydrothiophenium,1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiophenium,1-phenyltetrahydrothiopyranium,1-(4-hydroxyphenyl)tetrahydrothiopyranium,1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyranium and1-(4-methylphenyl)tetrahydrothiopyranium.

In formula (I-2), each of R⁵″ and R⁶″ independently represents an arylgroup or alkyl group. At least one of R⁵″ and R⁶″ represents an arylgroup. It is preferable that both of R⁵″ and R⁶″ represent an arylgroup.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

Specific examples of cation moiety represented by general formula (I-2)include diphenyliodonium and bis(4-tert-butylphenyl)iodonium.

Further, as a preferable example of the organic cation for Z⁺, a cationrepresented by general formula (I-5) or (I-6) shown below can also begiven.

In the formulas, R⁴⁰ represents a hydrogen atom or an alkyl group; R⁴¹represents an alkyl group, an acetyl group, a carboxy group or ahydroxyalkyl group; each of R⁴² to R⁴⁶ independently represents an alkylgroup, an acetyl group, an alkoxy group, a carboxy group, or ahydroxyalkyl group; each of n₀ to n₅ independently represents an integerof 0 to 3, with the provision that n₀+n₁ is 5 or less; and n₆ representsan integer of 0 to 2.

In general formulas (I-5) and (I-6), with respect to R⁴⁰ to R⁴⁶, thealkyl group is preferably an alkyl group of 1 to 5 carbon atoms, morepreferably a linear or branched alkyl group, and most preferably amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group or a tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

If there are two or more of the OR⁴⁰ group, as indicated by the value ofn₀, then the two or more of the OR⁴⁰ group may be the same or differentfrom each other.

If there are two or more of an individual R⁴¹ to R⁴⁶ group, as indicatedby the corresponding value of n₁ to n₆, then the two or more of theindividual R⁴¹ to R⁴⁶ group may be the same or different from eachother.

n₀ is preferably 0 or 1.

n₁ is preferably 0 to 2.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1.

As Z⁺, a cation moiety represented by general formula (I-1) or (I-5) ispreferable, and a cation moiety represented by any one of formulas(I-1-1) to (I-1-12) and (I-5-1) to (I-5-4) shown below is particularlydesirable. Among these, a cation moiety having a triphenyl skeleton,such as a cation moiety represented by any one of formulas (I-1-1) to(I-1-10) shown below is particularly desirable.

In general formulas (I-1-11) and (I-1-12), each of R⁹ and R¹⁹independently represents a phenyl group or a naphthyl group.

u is an integer of 1 to 3, and most preferably 1 or 2.

Among the aforementioned examples, as the component (B1), a compoundrepresented by general formula (b1-11) shown below is preferable.

In the formula, R¹″ to R³″, R^(0X) and r are the same as defined above.

Specific examples of preferable compounds as the component (B1) areshown below.

As the component (B1), one type of acid generator may be used alone, ortwo or more types may be used in combination.

In the positive resist composition of the present invention, the amountof the component (B1) relative to 100 parts by weight of the component(A) is preferably 0.1 to 40 parts by weight, more preferably 0.5 to 20parts by weight, and still more preferably 1 to 15 parts by weight. Whenthe amount of the component (B1) is at least as large as the lower limitof the above-mentioned range, the effects of the present invention canbe improved. On the other hand, when the amount of the component (B1) isno more than the upper limit of the above-mentioned range, thelithography properties are improved.

In the component (B), the amount of the component (B1) based on thetotal weight of the component (B) is preferably 3% by weight or more,more preferably 5 to 50% by weight, and still more preferably 7 to 35%by weight. When the amount of the component (B1) is at least as large asthe lower limit of the above-mentioned range, the effects of the presentinvention can be improved.

[Component (B2)]

In the positive resist composition of the present invention, if desired,the component (B) may further contain an acid generator other than thecomponent (B1) (hereafter, referred to as “component (B2)”).

The component (B2) is not particularly limited as long as it is an acidgenerator that does not fall under the category of the component (B1).Examples of such an acid generator are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators.

As an onium salt-based acid generator which does not fall under thecategory of the component (B1), a compound represented by generalformula (b-1) or (b-2) shown below can be used.

In formula (b-1), each of R¹″ to R³″ independently represents an arylgroup which may have a substituent or an alkyl group which may have asubstituent, with the provision that at least one of R¹″ to R³″represents an aryl group, and two of R¹″ to R³″ in formula (b-1) may bebonded to each other to form a ring with the sulfur atom. In formula(b-2), R⁵″ and R⁶″ each independently represent an aryl group which mayhave a substituent or an alkyl group which may have a substituent, withthe provision that and at least one of R⁵″ and R⁶″ represents an arylgroup. R⁴″ represents a halogenated alkyl group, an aryl group or analkenyl group which may have a substituent.

In general formula (b-1), R″ to R³″ are respectively the same as definedfor R¹″ to R³″ in general formula (I-1).

In general formula (b-2), R⁵″ and R⁶″ are respectively the same asdefined for R⁵″ and R⁶″ in general formula (I-2).

R⁴″ represents a halogenated alkyl group, an aryl group or an alkenylgroup which may have a substituent.

As an example of the halogenated alkyl group for R⁴″, a group in whichpart of or all of the hydrogen atoms of a linear, branched or cyclicalkyl group have been substituted with halogen atoms can be given.Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

When the alkyl group within the halogenated alkyl group is a linear orbranched alkyl group, it preferably has 1 to 10 carbon atoms, morepreferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.On the other hand, when the alkyl group within the halogenated alkylgroup is a cyclic alkyl group, it preferably has 4 to 15 carbon atoms,more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratios arepreferable, as they result in increased acid strength.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, and a group represented by the formula X-Q²- (in theformula, Q² represents a divalent linking group containing an oxygenatom; and X represents a hydrocarbon group of 3 to 30 carbon atoms whichmay have a substituent).

Examples of halogen atoms and alkyl groups as substituents for R⁴″include the same halogen atoms and alkyl groups as those described abovewith respect to the halogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X-Q²-, Q² represents a divalentlinking group containing an oxygen atom.

Q² may contain an atom other than an oxygen atom. Examples of atomsother than an oxygen atom include a carbon atom, a hydrogen atom, asulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate group(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, hetero atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³—O—C(═O)— (in theformulas, each of R⁹¹ to R⁹³ independently represents an alkylenegroup).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

As Q², a divalent linking group containing an ester bond or an etherbond is preferable, and —R⁹¹—O—, —R⁹²—O—C(═O)— or —C(═O)—O—R⁹³—O—C(═O)—is more preferable.

In the group represented by the formula X-Q²-, the hydrocarbon group forX may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X may be either a saturatedaliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbongroup. Further, the aliphatic hydrocarbon group may be linear, branchedor cyclic.

In the aliphatic hydrocarbon group for X, a part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or a part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for X, there is no particular limitation as long asit is an atom other than a carbon atom and a hydrogen atom. Examples ofhetero atoms include a halogen atom, an oxygen atom, a sulfur atom and anitrogen atom. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decanyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L5) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups asthose described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

Among the examples described above, as X, a cyclic group which may havea substituent is preferable. The cyclic group may be either an aromatichydrocarbon group which may have a substituent, or an aliphatic cyclicgroup which may have a substituent, and an aliphatic cyclic group whichmay have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by formulas (L2) to (L5), (S3) and (S4) are preferable.

Further, in the present invention, X preferably has a structure similarto that of the R³ group within the structural unit (a0) for thecomponent (A1), and a group having a polar portion is particularlydesirable, because it results in improved lithographic properties andresist pattern shape.

Specific examples of X having a polar moiety include those in which apart of the carbon atoms constituting the aliphatic hydrocarbon groupfor X is substituted with a substituent group containing a hetero atomsuch as —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (whereinH may be substituted with a substituent such as an alkyl group or anacyl group), —S—, —S(═O)₂— and —S(═O)₂—O—.

In the present invention, R⁴″ preferably has X-Q²- as a substituent. Inthis case, R⁴″ is preferably a group represented by formula X-Q²-Y³—[wherein Q² and X are the same as defined above; and Y³ represents analkylene group of 1 to 4 carbon atoms which may have a substituent, or afluorinated alkylene group of 1 to 4 carbon atoms which may have asubstituent].

In the group represented by the formula X-Q²-Y³—, as the alkylene groupfor Y³, the same alkylene group as those described above for Q² in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group for Y³, the aforementioned alkylenegroup in which part or all of the hydrogen atoms has been substitutedwith fluorine atoms can be used.

Specific examples of Y³ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y³ is preferably a fluorinated alkylene group, and particularlypreferably a fluorinated alkylene group in which the carbon atom bondedto the adjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represent an aryl groupor alkyl group. At least one of R⁵″ and R⁶″ represents an aryl group. Itis preferable that both of R⁵″ and R⁶″ represent an aryl group.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

As R⁴″ in formula (b-2), the same groups as those mentioned above forR⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented byformula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

Furthermore, onium salts in which the anion moiety of these onium saltsis replaced by an anion moiety represented by any one of formulas (b1)to (b8) shown below can also be used.

In the formulas, z0 represents an integer of 1 to 3; each of q1 and q2independently represents an integer of 1 to 5; q3 represents an integerof 1 to 12; t3 represents an integer of 1 to 3; each of r1 and r2independently represents an integer of 0 to 3; i represents an integerof 1 to 20; R⁷ represents a substituent; each of m1 to m5 independentlyrepresents 0 or 1; each of v0 to v5 independently represents an integerof 0 to 3; each of w1 to w5 independently represents an integer of 0 to3; and Q″ is the same as defined above.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor X may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w5, then the two or more of the R⁷ groups may be the sameor different from each other.

Among the aforementioned examples, in terms of significantly improvingthe effects of the present invention, the onium salt-based acidgenerator represented by formula (b-1) or (b-2) preferably has an anionmoiety in which a fluorine atom is bonded to a carbon atom adjacent tothe sulfur atom of the —SO₃ ⁻ group, more preferably an anion moiety inwhich R⁴″ represents a halogenated alkyl group which may have asubstituent, and most preferably an anion moiety represented by any oneof formulas (b1) to (b8).

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion moietyrepresented by general formula (b-3) or (b-4) shown below (the cationmoiety is the same as (b-1) or (b-2)) may also be used.

In the formulas, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkylgroup in which at least one hydrogen atom has been substituted with afluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The fluorination ratio of the alkylene group or alkyl group ispreferably from 70 to 100%, more preferably from 90 to 100%, and it isparticularly desirable that the alkylene group or alkyl group be aperfluoroalkylene group or perfluoroalkyl group in which all hydrogenatoms are substituted with fluorine atoms.

Further, onium salts having a cation moiety represented by generalformula (I-5) or (I-6) above, and having a fluorinated alkylsulfonateion (e.g., the anion moiety (R⁴″SO₃ ⁻) in general formula (b-1) or (b-2)above) or an anion moiety represented by general formula (b-3) or (b-4)above as the anion moiety, can be used.

In the present description, an oximesulfonate acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators includeα-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate acid generators disclosed in WO 2004/074242A2 (Examples1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B2), one type of acid generator may be used, or two ormore types may be used in combination.

In the positive resist composition of the present invention, the totalamount of the component (B) relative to 100 parts by weight of thecomponent (A) is preferably 0.5 to 50 parts by weight, and morepreferably 1 to 40 parts by weight. When the amount of the component (B)is within the above-mentioned range, formation of a resist pattern canbe satisfactorily performed. Further, by virtue of the above-mentionedrange, a uniform solution can be obtained and the storage stabilitybecomes satisfactory.

<Component (D)>

In the positive resist composition of the present invention, anitrogen-containing organic compound (D) (hereafter referred to as thecomponent (D)) may be added as an optional component.

As the component (D), there is no particular limitation as long as itfunctions as an acid diffusion control agent, i.e., a quencher whichtraps the acid generated from the component (B) upon exposure. Amultitude of these components (D) have already been proposed, and any ofthese known compounds may be used, although an aliphatic amine, andparticularly a secondary aliphatic amine or tertiary aliphatic amine ispreferable. An aliphatic amine is an amine having one or more aliphaticgroups, and the aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine is particularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

As the component (D), one type of compound may be used alone, or two ormore types may be used in combination.

In the present invention, as the component (D), it is preferable to usea trialkylamine of 5 to 10 carbon atoms.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

<Optional Components>

[Component (E)]

Furthermore, in the positive resist composition of the presentinvention, for preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, at least one compound (E) (hereafter referred to as the component(E)) selected from the group consisting of an organic carboxylic acid,or a phosphorus oxo acid or derivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

As the component (E), an organic carboxylic acid is preferable, andsalicylic acid is particularly desirable.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the positiveresist composition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

[Component (S)]

The positive resist composition of the present invention can be preparedby dissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, methyl-n-pentyl ketone, methylisopentyl ketone, 2-heptanone, a ketone having a 5-membered ring (e.g.,cyclopentanone, 2-methyl-2-cyclopenten-1-one, 2-methylcyclopentanone,3-methylcyclopentanone, 2-ethylcyclopentanone, 3-ethylcyclopentanone,2,2-dimethylcyclopentanone or 2,4,4-trimethylcyclopentanone), a ketonehaving a 6-membered ring (e.g., cyclohexanone, 2-cyclohexen-1-one,2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone,4-ethylcyclohexanone, 2,6-dimethylcyclohexanone or2,2-dimethylcyclohexanone) and a ketone having a 7-membered ring (e.g.,cycloheptanone, 2-cycloheptan-1-one and a polycyclic ketone having anorbornane skeleton or a norbornene skeleton, such as(1S,4R)-bicyclo[2.2.1]heptan-2-one); polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among the aforementioned examples, PGMEA, PGME, EL and cyclohexanone arepreferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

In addition, when a cyclic ketone such as cyclohexanone is used, theamount of the cyclic ketone within the component (S) is not particularlylimited, and can be appropriately selected depending on the type of thecyclic ketone. However, in terms of achieving excellent lithographyproperties, the amount of the cyclic ketone is preferably 1 to 80% byweight, more preferably 5 to 60% by weight, and still more preferably 10to 50% by weight.

The amount of the organic solvent is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 0.5 to 20% by weight, and preferably from 1 to 15% by weight.

Dissolving of the resist materials in the component (S) can be conductedby simply mixing and stirring each of the above components togetherusing conventional methods, and where required, the composition may alsobe mixed and dispersed using a dispersion device such as a dissolver, ahomogenizer, or a triple roll mill. Furthermore, following mixing, thecomposition may also be filtered using a mesh, or a membrane filter orthe like.

The positive resist composition of the present invention is advantageousin that a resist pattern having an excellent shape can be formed. Thereasons why these effects can be achieved has not been elucidated yet,but are presumed as follows.

The positive resist composition of the present invention includes apolymeric compound (A1) having an acid dissociable, dissolutioninhibiting group in the structure thereof and including a structuralunit (a0) represented by general formula (a0-1), and an acid generator(B1) containing a compound represented by general formula (b1-1).

The structural unit (a0) has a bulky structure in which a “cyclic groupcontaining —SO₂—” is bonded to the terminal of the side chain.Therefore, a resist film formed using the positive resist composition ofthe present invention exhibits a high glass transition temperature (Tg)as compared to the case of using no component (A1). When the Tg becomeshigh, the acid generated from the acid-generator component (B) uponexposure can be appropriately suppressed from diffusing within theresist film, and the acid can be suppressed from diffusing intounexposed portions.

Further, since the component (B1) has no fluorine atom bonded to acarbon atom adjacent to the sulfur atom of the —SO₃ ⁻ group, thecomponent (B1) generates a sulfonic acid exhibiting a weaker acidstrength than, for example, a sulfonic acid generated from the component(B2).

In the exposure during the formation of a resist pattern, it is presumedthat the amount of acid generated from the component (B) becomes largeras the light intensity becomes larger. It is presumed that the lightintensity becomes the largest along the central line of a space betweenlines in the case of a line and space pattern (hereafter, referred to as“LS pattern”), and at the central portion of a hole in the case of ahole resist pattern. When the generated acid is not suppressed fromdiffusing at the central portion, the acid is likely to be diffused tounexposed portions, so that unexposed portions near the central portionbecomes susceptible to being dissolved by alkali developing. As aresult, a resist pattern in which the central portion of the resistpattern (unexposed portion) has an hourglass shape is likely to beformed.

In the present invention, since an acid having a weak acid strength isgenerated from the component (B1) upon exposure, the acid dissociable,dissolution inhibiting group within the component (A) is lesssusceptible to being dissociated, as compared to the case where an acidhaving a strong acid strength is generated. Further, when the component(B1) is used in combination with the component (B2), a salt exchangeoccurs between the acid generated from the component (B1) and the acidgenerated from the component (B2). As a result, diffusion of the acidgenerated from the component (B2) is effectively suppressed by thecomponent (B1) (i.e., a quenching effect can be expected by the saltexchange). By virtue of the features described above, it is presumedthat, even when the light intensity and the amount of acid generated arethe largest near the aforementioned central portion, the amount ofstrong acid present in the entire space portions or holes is madeuniform, and hence, the acid dissociation reaction of the component (A)proceeds uniformly.

For the reasons as described above, by a positive resist composition inwhich the component (A1) and the component (B1) are used in combination,diffusion of the acid generated at exposed portions to the unexposedportions can be reliably suppressed, and the acid dissociation reactionis made uniform at the entire exposed portions. As a result, it ispresumed that a resist pattern having a high rectangularity can beformed.

Moreover, by using the resist composition of the present invention, ahole pattern having high circularity can be formed. Also, a hole patternhaving no white band of unevenness around the periphery of the holes canbe formed. In addition, the uniformity (CDU) of the hole diameter (CD)is improved, and as a result, a resist pattern having an excellent shapeand high circularity can be formed even with a narrow pitch.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to a second aspect ofthe present invention includes: applying a positive resist compositionof the present invention to a substrate to form a resist film on thesubstrate; conducting exposure of the resist film; and alkali-developingthe resist film to form a resist pattern.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.Firstly, a positive resist composition of the present invention isapplied onto a substrate using a spinner or the like, and a prebake(post applied bake (PAB)) is conducted under temperature conditions of80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds to forma resist film. Then, for example, using an ArF exposure apparatus or thelike, the resist film is selectively exposed with an ArF exposureapparatus, an electron beam exposure apparatus, an EUV exposureapparatus or the like through a mask pattern or directly irradiated withelectron beam without a mask pattern, followed by post exposure bake(PEB) under temperature conditions of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds. Subsequently, developing isconducted using an alkali developing solution such as a 0.1 to 10% byweight aqueous solution of tetramethylammonium hydroxide (TMAH),preferably followed by rinsing with pure water, and drying. If desired,bake treatment (post bake) can be conducted following the developing. Inthis manner, a resist pattern that is faithful to the mask pattern canbe obtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm.

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The positive resist composition of the present invention iseffective to KrF excimer laser, ArF excimer laser, EB and EUV, andparticularly effective to ArF excimer laser.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long at it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

The method of forming a resist pattern according to the presentinvention is also applicable to a double exposure method or a doublepatterning method.

EXAMPLES

As follows is a description of examples of the present invention,although the scope of the present invention is by no way limited bythese examples.

In the following examples, a unit represented by a chemical formula (1)is designated as “compound (1)”, and the same applies for compoundsrepresented by other formulas.

<Base Component (A)>

The polymeric compounds used as the base component (A) in the presentexamples were synthesized in accordance with the following polymersynthesis examples using the compounds (1) to (9) represented by thechemical formulas shown below.

The compound (1) used in the polymer synthesis examples was synthesizedin accordance with the monomer synthesis example described below.

Monomer Synthesis Example 1

Synthesis of Compound (1)

300 ml of a THF solution containing 20 g (105.14 mmol) of an alcohol(1), 30.23 g (157.71 mmol) of ethyldiisopropylaminocarbodiimide (EDCI)hydrochloride and 0.6 g (5 mmol) of dimethylaminopyridine (DMAP) wasadded to a 500 ml three-necked flask in a nitrogen atmosphere, and 16.67g (115.66 mmol) of a precursor (1) was added thereto while cooling withice (0° C.), followed by stirring at room temperature for 12 hours.

After conducting thin-layer chromatography (TLC) to confirm that the rawmaterials had been consumed, 50 ml of water was added to stop thereaction. Then, the reaction solvent was concentrated under reducedpressure, and extraction was conducted with ethyl acetate three times.The obtained organic phase was washed with water, saturated sodiumhydrogencarbonate and 1N—HClaq in this order. Thereafter, the solventwas distilled off under reduced pressure, and the resulting product wasdried, thereby obtaining the compound (1).

The results of instrumental analysis of the obtained compound (1) wereas follows.

¹H-NMR (CDCl₃, 400 MHz): δ(ppm)=6.22 (s, 1H, H^(a)), 5.70 (s, 1H,H^(b)), 4.71-4.85 (m, 2H, H^(k)), 4.67 (s, 2H, H^(k)), 3.40-3.60 (m, 2H,H^(e,f)), 2.58-2.70 (m, 1H, H^(g)), 2.11-2.21 (m, 2H, H^(h)), 2.00 (s,3H, H^(i)), 1.76-2.09 (m, 2H, H^(j))

From the results shown above, it was confirmed that the compound (1) hada structure shown below.

Polymer Synthesis Example 1 Synthesis of Polymeric Compound (1)

In a three-necked flask equipped with a thermometer and a reflux tube,11.77 g (69.23 mmol) of a compound (7), 15.00 g (47.47 mmol) of acompound (1), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69mmol) of a compound (5) and 3.27 g (13.85 mmol) of a compound (9) weredissolved in 76.91 g of methyl ethyl ketone (MEK) to obtain a solution.Then, 22.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name:V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was addedand dissolved in the obtained solution. The resultant was dropwise addedto 42.72 g of MEK heated to 78° C. in a nitrogen atmosphere over 3hours. Thereafter, the reaction solution was heated for 4 hour whilestirring, and then cooled to room temperature. The obtained reactionpolymer solution was dropwise added to an excess amount of n-heptane,and an operation to deposit a polymer was conducted. Thereafter, theprecipitated white powder was separated by filtration, followed bywashing with a n-heptane/isopropylalcohol mixed solvent and drying,thereby obtaining 41 g of a polymeric compound (1) as an objectivecompound.

With respect to the polymeric compound (1), the weight average molecularweight (Mw) and the dispersity (Mw/Mn) were determined by thepolystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight was 7,900, and the dispersity was 1.78. Further, as aresult of an analysis by carbon 13 nuclear magnetic resonancespectroscopy (600 MHz, ¹³C-NMR), it was found that the composition ofthe copolymer (ratio (molar ratio) of the respective structural unitswithin the structural formula) was a21/a0/a12/a14/a3=35/27/18/13/7.

Polymer Synthesis Examples 2 to 8 Synthesis of Polymeric Compounds (2)to (8)

Other polymeric compounds (2) to (8) were synthesized in substantiallythe same manner as in Polymer Synthesis Example 1, except that monomersfor deriving the structural units of the respective polymeric compoundswere used in a predetermined molar ratio.

The structural formulas of the obtained polymeric compounds (2) to (8),the weight average molecular weight (Mw) and the molecular weightdispersity (Mw/Mn) as determined by the polystyrene equivalent value asmeasured by gel permeation chromatography (GPC) and the compositionalratios of the copolymers as measured by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR) are shown below.

[Mw 7000, Mw/Mn 1.8; a21/a0/a11/a14/a3=35/25/19/12.5/7.5]

Polymeric Compound (3)

[Mw 7000, Mw/Mn 1.8; a21/a0/a12/a14/a3=36/21/18/13/12]

Polymeric Compound (4)

[Mw 7900, Mw/Mn 1.78; a21/a0/a12/a14/a3=35/21/24/13/7]

[Mw 8000, Mw/Mn 1.8; a21/a0/a13/a11/a3=30/25/25/10/10]

[Mw 8000, Mw/Mn 1.8; a21/a22/a13/a11/a3=30/25/25/10/10]

[Mw 8000, Mw/Mn 1.8; a0/a15/a3=50/30/20]

[Mw 8000, Mw/Mn 1.8; a21/a15/a3=50/30/20]

<Synthesis of Acid-Generator Component (B)>

The acid generators used as the acid-generator component (B) in thepresent examples were synthesized in accordance with the followingacid-generator synthesis examples.

[Acid-Generator Synthesis Example 1: Synthesis of Acid Generator (1)]

(i) Synthesis of Compound (IV)

150 g of methyl fluorosulfonyl(difluoro)acetate and 375 g of pure waterwere maintained at 10° C. or lower in an ice bath, and 343.6 g of a 30%by weight aqueous solution of sodium hydroxide was dropwise addedthereto. Then, the resultant was refluxed at 100° C. for 3 hours,followed by cooling and neutralizing with a concentrated hydrochloricacid. The resulting solution was dropwise added to 8,888 g of acetone,and the precipitate was collected by filtration and dried, therebyobtaining 184.5 g of a compound (I) in the form of a white solid(purity: 88.9%, yield: 95.5%).

Subsequently, 56.2 g of the compound (I) and 562.2 g of acetonitrilewere prepared, and 77.4 g of p-toluenesulfonic acid monohydrate wasadded thereto. The resultant was refluxed at 110° C. for 3 hours. Then,the reaction mixture was filtered, and the filtrate was concentrated anddried to obtain a solid. 900 g of t-butyl methyl ether was added to theobtained solid and stirred. Thereafter, the resultant was filtered, andthe residue was dried, thereby obtaining 22.2 g of a compound (II) inthe form of a white solid (purity: 91.0%, yield: 44.9%).

Subsequently, 4.34 g of the compound (II) (purity: 94.1%), 3.14 g of2-benzyloxyethanol and 43.4 g of toluene were prepared, and 0.47 g ofp-toluenesulfonic acid monohydrate was added thereto. The resultant wasrefluxed at 105° C. for 20 hours. Then, the reaction mixture wasfiltered, and 20 g of hexane was added to the residue and stirred.Thereafter, the resultant was filtered, and the residue was dried,thereby obtaining 1.41 g of a compound (III) (yield: 43.1%).

The obtained compound (III) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=4.74-4.83 (t, 1H, OH), 4.18-4.22 (t,2H, H^(a)), 3.59-3.64 (q, 2H, H^(b))

¹⁹F-NMR (DMSO-d6, 376 MHz): δ(ppm)=−106.6

From the results shown above, it was confirmed that the compound (III)had a structure shown below.

Next, 1.00 g of the compound (III) and 3.00 g of acetonitrile wereprepared, and 0.82 g of 1-adamantanecarbonyl chloride and 0.397 g oftriethylamine were dropwise added thereto while cooling with ice. Then,the resultant was stirred at room temperature for 20 hours, followed byfiltration. The filtrate was concentrated and dried, and dissolved in 30g of dichloromethane, followed by washing with water three times.Thereafter, the organic phase was concentrated and dried, therebyobtaining 0.82 g of a compound (IV) (yield: 41%).

The obtained compound (IV) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=8.81 (s, 1H, H^(c)), 4.37-4.44 (t, 2H,H^(d)), 4.17-4.26 (t, 2H, H^(e)), 3.03-3.15 (q, 6H, H^(b)), 1.61-1.98(m, 15H, Adamantane), 1.10-1.24 (t, 9H, H^(a))

¹⁹F-NMR (DMSO-d6, 376 MHz): δ(ppm)=−106.61

From the results above, it was confirmed that the compound (IV) had astructure shown below.

(ii) Synthesis of Acid Generator (1)

2 g of the compound (V) was added to 20 g of dichloromethane and 20 g ofwater, followed by stirring. Then, 2.54 g of the compound (IV) was addedthereto, followed by stirring for 1 hour. The reaction mixture wassubjected to liquid separation, and the resultant was washed four timeswith 20 g of water. After the washing, the organic solvent phase wasconcentrated and solidified, thereby obtaining 2.3 g of an acidgenerator (1).

The obtained acid generator (1) was analyzed by NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=7.72-7.83 (m, 10H, Ar), 7.72 (s, 2H,Ar), 6.49-6.55 (m, 1H, Vinyl), 4.37-4.44 (t, 2H, CH₂), 4.20-4.23 (d, 1H,Vinyl), 4.00-4.26 (m, 7H, CH₂+Vinyl), 2.27 (s, 6H, CH₃), 1.61-1.98 (m,15H, Adamantane)

¹⁹F-NMR (DMSO-d6, 376 MHz): δ(ppm)=−106.61

From the results shown above, it was confirmed that the acid generator(1) had a structure shown below.

[Acid-Generator Synthesis Example 2: Synthesis of Acid Generator (4)]

(i) Synthesis of Compound (d)

5.00 g of the compound (II), 5.68 g of sultone-OH (c) and 100 g oftoluene were prepared, and 0.43 g of p-toluenesulfonic acid monohydratewas added thereto. The resultant was heated until toluene was refluxed,and a reaction was effected in this state for 65 hours. Thereafter, thereaction mixture was filtered, and 100 g of toluene was added to theresidue, followed by stirring at room temperature for 10 minutes. Thisfiltration step was performed twice to obtain a black powder. Theobtained powder was dried under reduced pressure for one night, andextraction was conducted twice using 100 g of acetone. Then, acetone wasdistilled off from the filtrate, and the resultant was dissolved in 30 gof acetone to obtain a solution. The obtained solution was graduallyadded to a mixture of 300 g of TBME and 300 g of methylene chloride in adropwise manner, and the precipitated solid was collected by filtrationand dried, thereby obtaining 6.88 g of a compound (d) in the form of awhite powder (yield: 78.4%).

The obtained compound (d) was analyzed by ¹H-NMR and ¹⁹F-NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm) 1.73-2.49 (m, 4H, Ha, Hb), 2.49 (m,1H, Hc), 3.48 (m, 1H, Hd), 3.88 (t, 1H, He), 4.66 (t, 1H, Hf), 4.78 (m,1H, Hg)

¹⁹F-NMR (DMSO-d6, 400 MHz): δ(ppm) −107.7 (m, 2F, Fa) (the peak ofhexafluorobenzene was regarded as −160 ppm)

From the results above, it was confirmed that the compound (d) had astructure shown below.

(ii) Synthesis of Intermediate Compound (f-01)

To 60.75 g of methanesulfonic acid controlled to 20° C. or lower wasadded 8.53 g of phosphorus oxide, 8.81 g of 2,6-dimethylphenol and 12.2g of diphenylsulfoxide in small amounts. The resultant was matured for30 minutes while maintaining the temperature at 15 to 20° C., followedby elevating the temperature to 40° C. and maturing for 2 hours. Then,the reaction mixture was dropwise added to 109.35 g of pure water cooledto 15° C. or lower. Thereafter, 54.68 g of dichloromethane was added andstirred, and the dichloromethane phase was collected. 386.86 g of hexaneat a temperature of 20 to 25° C. was added to a separate vessel, and thedichloromethane phase was dropwise added thereto. Then, the resultantwas matured at 20 to 25° C. for 30 minutes, followed by filtration,thereby obtaining an intermediate compound (f-01) as an objectivecompound (yield: 70.9%).

The obtained intermediate compound (f-01) was analyzed by ¹H-NMR.

¹H-NMR (DMSO-d6, 600 MHz): δ(ppm)=7.61-7.72 (m, 10H, phenyl), 7.14 (S,2H, H^(c)), 3.12 (S, 3H, H^(b)), 2.22 (s, 6H, H^(a))

From the results shown above, it was confirmed that the obtainedintermediate compound (f-01) had a structure shown below.

(iii) Synthesis of Compounds (f-1) to (f-3)

4 g of the intermediate compound (f-01) was dissolved in 79.8 g ofdichloromethane. After confirming that the compound (i) had dissolved indichloromethane, 6.87 g of potassium carbonate was added thereto, and3.42 g of 2-methyl-2-adamantyl bromoacetate was further added. Areaction was effected under reflux for 24 hours, followed by filtration,washing with water, and crystallization with hexane. The resultingpowder was dried under reduced pressure, thereby obtaining 3.98 g of anobjective compound (yield: 66%).

The obtained objective compound was analyzed by ¹H-NMR. The results areshown below.

¹H-NMR (CDCl₃, 600 MHz): δ(ppm)=7.83-7.86 (m, 4H, phenyl), 7.69-7.78 (m,6H, phenyl), 7.51 (s, 2H, Hd), 4.46 (s, 2H, Hc), 2.39 (s, 6H, Ha), 2.33(s, 2H, Adamantane), 2.17 (s, 2H, Adamantane), 1.71-1.976 (m, 11H,Adamantane), 1.68 (s, 3H, Hb), 1.57-1.61 (m, 2H, Adamantane)

From the results of the analysis shown above, it was confirmed that theobjective compound contained a compound (f-1) having a structure shownbelow.

Further, as a result of an ion chromatography analysis, it was confirmedthat the obtained objective compound also contained a compound (f-2) anda compound (f-3), both of which had the same NMR data for the cationmoiety as that of the compound (f-1). The amounts of the compound (f-1),the compound (f-2) and the compound (f-3) were 21.4 mol %, 11.4 mol %and 67.2 mol %, respectively.

(iv) Synthesis of Acid Generator (4)

5.00 g of the compound (d) was dissolved in 50.0 g of pure water, and6.19 g of the compound (f-3) and 50.0 g of methylene chloride were addedthereto in this order, followed by stirring at room temperature for 10hours. Then, the organic phase was collected from the resultant byliquid separation. Thereafter, the organic phase was washed three timeswith a 1% aqueous HCl solution, once with a 1% aqueous ammonia solutionand four times with pure water, and the organic phase was concentrated,thereby obtaining 8.58 g of an acid generator (4) in the form of a whitesolid (90.4%).

The obtained acid generator (4) was analyzed by ¹H-NMR and ¹⁹F-NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm)=1.47-1.95 (m, 15H, Ad, 3H, anion),2.13-2.16 (m, 2H, Ad, 1H, anion), 2.30 (s, 6H, PhCH₃), 2.49 (m, 1H,anion), 3.48 (m, 1H, anion), 3.88 (t, 1H, anion), 4.58 (s, 2H, CH₂) 4.66(t, 1H, anion), 4.78 (m, 1H, anion), 7.57 (m, 2H, Ph), 7.72-7.84 (m,10H, Ph)

¹⁹F-NMR (DMSO-d6, 400 MHz): δ(ppm) −107.8 (m, 2F, CF₂) (the peak ofhexafluorobenzene was regarded as −160 ppm)

From the results shown above, it was confirmed that the acid generator(4) had a structure shown above.

[Acid-Generator Synthesis Example 3: Synthesis of Acid Generator (5)]

3.21 g of the compound (d) was added to 32.1 g of pure water, and 3.72 gof 4-methylphenyldiphenylsulfonium bromide and 32.1 g of methylenechloride were added thereto in this order, followed by stirring at roomtemperature for 1 hour. Then, the organic phase was collected from theresultant by liquid separation. Thereafter, the organic phase was washedthree times with a 1% aqueous HCl solution, and four times with purewater, and the organic phase was concentrated, thereby obtaining 4.94 gof an acid generator (5) in the form of a white solid (86.8%).

The obtained acid generator (5) was analyzed by ¹H-NMR and ¹⁹F-NMR.

¹H-NMR (DMSO-d6, 400 MHz): δ(ppm) 1.74-2.21 (m, 4H, anion), 2.41 (t, 3H,PhCH₃), 2.58 (m, 1H, anion), 3.48 (m, 1H, anion), 3.87 (t, 1H, anion),4.66 (t, 1H, anion), 4.78 (m, 1H, anion), 7.58 (m, 2H, ph), 7.64-7.84(m, 12H, ph)

¹⁹F-NMR (DMSO-d6, 400 MHz): δ(ppm) −107.6 (m, 2F, Fa) (the peak ofhexafluorobenzene was regarded as −160 ppm)

From the results shown above, it was confirmed that the acid generator(5) had a structure shown above.

<Production of Positive Resist Composition>

The components shown in Tables 1 to 3 were mixed together and dissolvedto obtain positive resist compositions. In the tables, “-” indicatesthat the component was not added.

TABLE 1 Component Component Component Component (A) Component (B) (D)(E) (S) Comp. Ex. 1 (A)-6 (B)-1 (B)-2 (D)-1 (E)-1 (S)-1 [100] [6.7][2.6] [0.15] [0.24] [2900] Comp. Ex. 2 (A)-5 (B)-1 — (D)-1 (E)-1 (S)-1[100] [6.7] [0.15] [0.24] [2900] Ex. 1 (A)-5 (B)-1 (B)-2 (D)-1 (E)-1(S)-1 [100] [6.7] [2.6] [0.15] [0.24] [2900] Ex. 2 (A)-2 (B)-1 (B)-2(D)-1 (E)-1 (S)-1 [100] [6.7] [2.6] [0.15] [0.24] [2900] Ex. 3 (A)-3(B)-1 (B)-2 (D)-1 (E)-1 (S)-1 [100] [6.7] [2.6] [0.15] [0.24] [2900]

TABLE 2 Component Component Component Component (A) Component (B) (D)(E) (S) Comp. Ex. 3 (A)-4 (B)-3 — (D)-1 — (S)-2 [100] [9.8] [0.4] [3200] Ex. 4 (A)-4 (B)-3 (B)-2 (D)-1 (E)-1 (S)-2 [100] [9.8] [1.3][0.2]  [0.4] [3200] Comp. Ex. 4 (A)-4 (B)-4 — (D)-1 (E)-1 (S)-2 [100][10.1]  [0.3]  [0.4] [3200] Ex. 5 (A)-4 (B)-4 (B)-2 (D)-1 (E)-1 (S)-2[100] [10.1]  [1.3] [0.15] [0.4] [3200] Ex. 6 (A)-4 (B)-5 (B)-2 (D)-1(E)-1 (S)-2 [100] [7.3] [1.3] [0.15] [0.4] [3200] Ex. 7 (A)-4 (B)-5(B)-2 (D)-1 (E)-1 (S)-2 [100]  [6.35] [1.3] [0.15] [0.4] [3200] Ex. 8(A)-1 (B)-5 (B)-2 (D)-1 (E)-1 (S)-2 [100]  [6.35] [1.3] [0.15]  [0.24][3200]

TABLE 3 Component Component (A) Component (B) (S) Comp. Ex. 5 (A)-8(B)-7 (B)-8 (B)-6 (S)-1 [100] [3.5] [1.0] [1.0] [2400] Comp. Ex. 6 (A)-7(B)-7 (B)-8 — (S)-1 [100] [3.5] [1.0] [2400] Ex. 9 (A)-7 (B)-7 (B)-8(B)-2 (S)-1 [100] [3.5] [1.0] [1.0] [2400] Ex. 10 (A)-7 (B)-7 (B)-8(B)-6 (S)-1 [100] [3.5] [1.0] [1.0] [2400]

In Tables 1 to 3, the reference characters indicate the following.Further, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added.

(A)-1: the aforementioned polymeric compound (1)

(A)-2: the aforementioned polymeric compound (2)

(A)-3: the aforementioned polymeric compound (3)

(A)-4: the aforementioned polymeric compound (4)

(A)-5: the aforementioned polymeric compound (5)

(A)-6: the aforementioned polymeric compound (6)

(A)-7: the aforementioned polymeric compound (7)

(A)-8: the aforementioned polymeric compound (8)

(B)-1: the aforementioned acid generator (1)

(B)-2: an acid generator (2) represented by chemical formula (B1-1)shown below

(B)-3: an acid generator (3) represented by chemical formula (B2-1)shown below

(B)-4: the aforementioned acid generator (4)

(B)-5: the aforementioned acid generator (5)

(B)-6: an acid generator (6) represented by chemical formula (B1-2)shown below

(B)-7: (4-methylphenyl)diphenylsulfonium nonafluoro-n-butanesulfonate

(B)-8: (4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate

(D)-1: tri-n-pentylamine

(E)-1: salicylic acid

(S)-1: a mixed solvent of PGMEA/PGME/cyclohexanone=45/30/25 (weightratio)

(S)-2: a mixed solvent of PGMEA/PGME=6/4 (weight ratio)

<Evaluation of Resist Pattern>

Using the obtained positive resist compositions, resist patterns wereformed in the following manner, and the shape of the resist patterns wasevaluated.

Examples 1 to 3 Comparative Examples 1 and 2 [Formation of ResistPattern by Immersion Exposure](1)

An organic anti-reflection film composition (product name: ARC95,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 90 nm.

Then, each of the positive resist compositions obtained in Examples 1 to3 and Comparative Examples 1 and 2 was applied to the organicanti-reflection film using a spinner, and was then prebaked (PAB) on ahotplate at 110° C. for 60 seconds and dried, thereby forming a resistfilm having a film thickness of 90 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography(product name: NSR-S609B, manufactured by Nikon Corporation, NA(numerical aperture)=1.07, σ0.97), the resist film having a top coatformed thereon was selectively irradiated with an ArF excimer laser (193nm) through a mask pattern for forming a hole pattern.

Next, a post exposure bake (PEB) treatment was conducted at 95° C. for60 seconds, followed by alkali development for 30 seconds at 23° C. in a2.38% by weight aqueous TMAH solution (product name: NMD-3; manufacturedby Tokyo Ohka Kogyo Co., Ltd.). Then, the resist was washed for 25seconds with pure water, followed by drying by shaking.

As a result, in each of the examples, a line and space pattern(hereafter, referred to as “LS pattern”) having a line width of 50 nmand a pitch of 100 nm was formed.

[Sensitivity]

The optimum exposure dose Eop (mJ/cm²; sensitivity) with which the LSpattern having a line width of 50 nm and a pitch of 100 nm was formed inthe “Formation of resist pattern (1)” was determined. The results areshown in Table 4.

[Evaluation of Resist Pattern Shape]

Each of the LS patterns having a line width of 50 nm and a pitch of 100nm and formed with the above Eop was observed using a scanning electronmicroscope (SEM), and the cross-sectional shape of the LS pattern wasevaluated. The results are shown in Table 4.

TABLE 4 Eop Shape of LS (mJ/cm²) resist pattern Comp. Ex. 1 30.1 Slightfooting Comp. Ex. 2 20.1 Hourglass Ex. 1 32.0 Rectangular Ex. 2 27.4Rectangular Ex. 3 25.4 Rectangular

From the results shown in Table 4, it was confirmed that the positiveresist compositions of Examples 1 to 3 were capable of forming a resistpattern having an excellent rectangularity and an excellent shape, ascompared to the resist patterns formed using the positive resistcompositions of Comparative Examples 1 and 2.

Examples 4 to 8 Comparative Examples 3 and 4

[Formation of Resist Pattern by Immersion Exposure](2)

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm.

Then, each of the positive resist compositions obtained in Examples 4 to8 and Comparative Examples 3 and 4 was applied to the anti-reflectionfilm using a spinner, and was then prebaked (PAB) on a hotplate at atemperature indicated in Table 5 for 60 seconds and dried, therebyforming a resist film having a film thickness of 100 nm.

Subsequently, a coating solution for forming a protection film (productname: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was appliedto the resist film using a spinner, and then heated at 90° C. for 60seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography(product name: NSR-S609B, manufactured by Nikon Corporation, NA(numerical aperture)=1.07, σ0.97), the resist film having a top coatformed thereon was selectively irradiated with an ArF excimer laser (193nm) through a mask pattern.

Next, a post exposure bake (PEB) treatment was conducted at atemperature indicated in Table 5 for 60 seconds, followed by developmentfor 30 seconds at 23° C. in a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) (product name: NMD-3; manufacturedby Tokyo Ohka Kogyo Co., Ltd.). Then, the resist film was rinsed for 30seconds with pure water, followed by drying by shaking.

As a result, in each of the examples, a contact hole pattern in whichholes having a diameter of 90 nm were equally spaced (pitch: 540 nm) wasformed (hereafter, this contact hole pattern is referred to as “Iso CHpattern”).

Subsequently, hole patterns were formed in the same manner as in the“Formation of resist pattern by immersion exposure (2)”, except that thePAB treatment and the PEB treatment were conducted at the temperaturesindicated in Table 6.

As a result, in each of the examples, a contact hole pattern in whichholes having a diameter of 90 nm were equally spaced (pitch: 140 nm) wasformed (hereafter, this contact hole pattern is referred to as “NestedCH pattern”).

Evaluation of Iso CH Pattern

[Sensitivity]

The optimum exposure dose Eop (mJ/cm²; sensitivity) with which the IsoCH patterns having a hole diameter of 90 nm and a pitch of 540 nm wasformed in the “Formation of resist pattern (2)” was determined. Theresults are shown in Table 5.

[Evaluation of CD Uniformity (CDU)]

With respect to each of the Iso CH patterns formed with the above Eop,the hole diameter (CD) of 25 holes were measured. From the results, thevalue of 3 times the standard deviation σ (i.e., 30 was calculated as ayardstick of CD uniformity (CDU). The results are shown in Table 5.

The smaller this 3σ value is, the higher the level of CDU of the holesformed in the resist film.

[Evaluation of Circularity]

Each of the Iso CH patterns formed above was observed from the upperside thereof using a scanning electron microscope (SEM) (product name:S-9220, manufactured by Hitachi, Ltd.), and the circularity wasevaluated with the following criteria. The results are shown in Table 5.

A: Almost no unevenness was observed at the circumferential portions ofthe holes, and the circularity of the holes was exceptionally good

B: Only small degree of unevenness was observed at the circumferentialportions of the holes, and the circularity of the holes was excellent

TABLE 5 PAB PEB Eop Iso (° C.) (° C.) (mJ/cm²) CDU Circularity Comp. Ex.3 90 85 29.7 5.64 B Ex. 4 90 85 33.7 5.27 A Comp. Ex. 4 90 85 33.0 4.86B Ex. 5 90 85 38.8 4.72 A Ex. 6 90 85 28.9 4.29 A Ex. 7 90 85 39.8 4.61A Ex. 8 110 85 49.4 4.38 A

Evaluation of Nested CH Pattern

With respect to the Nested CH patterns formed above, the sensitivity,the CD uniformity (CDU) and the circularity were evaluated in the samemanner as in the evaluation of the Iso CH patterns. The results areshown in Table 6.

TABLE 6 PAB PEB Eop Nested (° C.) (° C.) (mJ/cm²) CDU Circularity Comp.Ex. 3 90 85 28.7 5.39 B Ex. 4 90 85 32.1 6.62 A Comp. Ex. 4 90 85 33.15.93 B Ex. 5 90 85 37.4 5.90 A Ex. 6 90 85 28.2 5.84 A Ex. 7 90 85 38.44.41 A Ex. 8 110 85 47.0 5.89 A

As seen from the results shown in Tables 5 and 6, with respect to thepositive resist compositions of Examples 4 to 8 according to the presentinvention, high circularity and an excellent shape could be achieved forboth the Iso CH pattern and the Nested CH pattern (i.e., both isolatedhole pattern and dense hole pattern), as compared to the Iso CH patternand the Nested CH pattern formed using the positive resist compositionsof Comparative Examples 3 and 4.

Further, it was confirmed that the positive resist compositions ofExamples 4 to 8 exhibited about the same level of CDU as that of thepositive resist compositions of Comparative Examples 3 and 4.

Therefore, it is presumed that for both of an isolated hole pattern anda dense hole pattern, the acid dissociation reaction of the component(A) proceeds uniformly by virtue of the positive resist composition ofthe present invention including a polymeric compound (A1) having an aciddissociable, dissolution inhibiting group in the structure thereof andincluding a structural unit (a0) represented by general formula (a0-1),and an acid generator (B1).

Examples 9 and 10 Comparative Examples 5 and 6

Formation of Resist Pattern (3)

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied to an 8-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 77 nm.

Then, each of the positive resist composition obtained in Examples 9 and10 and Comparative Examples 5 and 6 was applied to the anti-reflectionfilm using a spinner, and was then prebaked (PAB) on a hotplate at 115°C. for 60 seconds and dried, thereby forming a resist film having a filmthickness of 150 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern, using an ArF exposureapparatus NSR-S306 (manufactured by Nikon Corporation; NA (numericalaperture)=0.78, ⅔ annular illumination).

Thereafter, a post exposure bake (PEB) treatment was conducted at 115°C. for 60 seconds, followed by development for 30 seconds at 23° C. in a2.38% by weight aqueous tetramethylammonium hydroxide (TMAH) solution(product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then,the resist film was washed for 30 seconds with pure water, followed bydrying by shaking.

As a result, in each of the examples, a line and space pattern (LSpattern) having a line width of 85 nm and a pitch of 170 nm was formedon the resist film.

[Sensitivity]

The optimum exposure dose Eop (mJ/cm²; sensitivity) with which the LSpattern having a line width of 85 nm and a pitch of 170 nm was formed inthe “Formation of resist pattern (3)” was determined. The results areshown in Table 7.

[Evaluation of Resist Pattern Shape]

Each of the LS patterns having a line width of 85 nm and a pitch of 170nm and formed with the above Eop was observed using a scanning electronmicroscope (SEM), and the cross-sectional shape of the LS pattern wasevaluated with the following criteria. The results are shown in Table 7.

TABLE 7 Eop Shape of LS (mJ/cm²) resist pattern Comp. Ex. 5 33.0 FootingComp. Ex. 6 26.0 Footing Ex. 9 38.0 Rectangular Ex. 10 37.0 Rectangular

From the results shown in Table 4, it was confirmed that the positiveresist compositions of Examples 9 and 10 were capable of forming aresist pattern having an excellent rectangularity and an excellentshape, as compared to the resist patterns formed using the positiveresist compositions of Comparative Examples 5 and 6.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

1. A positive resist composition comprising a base component (A) whichexhibits increased solubility in an alkali developing solution underaction of acid and an acid-generator component (B) which generates acidupon exposure, the base component (A) comprising a polymeric compound(A1) having an acid dissociable, dissolution inhibiting group in thestructure thereof and comprising a structural unit (a0) represented bygeneral formula (a0-1) shown below, and the acid-generator component (B)comprising an acid generator (B1) comprised of a compound represented bygeneral formula (b1-1) shown below:

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; R² representsa divalent linking group; and R³ represents a cyclic group containing an—SO₂— group within the ring skeleton thereof; and[Chemical Formula 2]R⁰—SO₃ ⁻Z⁺  (b1-1) wherein R⁰ represents a hydrocarbon group of 1 to 12carbon atoms which may have a substituent, with the provision that thecarbon atom adjacent to the sulfur atom within the —SO₃ ⁻ group has nofluorine atom bonded thereto; and Z⁺ represents an organic cation. 2.The positive resist composition according to claim 1, wherein R³ ingeneral formula (a0-1) represents a cyclic group containing an —O—SO₂—group within the ring skeleton thereof.
 3. The positive resistcomposition according to claim 2, wherein R³ in general formula (a0-1)is a cyclic group represented by general formula (3-1) shown below:

wherein A′ represents an oxygen atom, a sulfur atom, or an alkylenegroup of 1 to 5 carbon atoms which may contain an oxygen atom or asulfur atom; p represents an integer of 0 to 2; and R⁸ represents analkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.
 4. The positive resistcomposition according to claim 1, wherein the polymeric compound (A1)further comprises a structural unit (a1) derived from an acrylate estercontaining an acid dissociable, dissolution inhibiting group, exclusiveof the structural unit (a0).
 5. The positive resist compositionaccording to claim 1, wherein the polymeric compound (A1) furthercomprises a structural unit (a2) derived from an acrylate estercontaining a lactone-containing cyclic group.
 6. The positive resistcomposition according to claim 1, wherein the polymeric compound (A1)further comprises a structural unit (a3) derived from an acrylate estercontaining a polar group-containing aliphatic hydrocarbon group.
 7. Thepositive resist composition according to claim 1, which furthercomprises a nitrogen-containing organic compound (D).
 8. A method offorming a resist pattern, comprising: forming a resist film using apositive resist composition of claim 1; conducting exposure of saidresist film; and alkali-developing said resist film to form a resistpattern.